"Modular, composable web components. Modular, composable styles."
Gem.js is a view library - a set of extensible web components for building visual user interfaces and styling web applications in pure-javascript.
The power of functions and variables is unparalleled, and yet languages like HTML and CSS, which don't have any ability to compose structures together, are still the primary ways people build web applications. Framework after framework has come along to try and solve the problem of making web pages dynamic. Angular, Backbone, Ember, jQuery, mooTools, Dojo, YUI, etc have all tried to be everything to everyone. But what they fail at providing is simplicity and modularity. They end up with bloated libraries filled with features you're not using.
Gem.js is here to change that. Finally, modern application development for the browser!
Gem.js?Gem.js is notvar Button = require("gem/Button")
var Style = require("gem/Style")
var Block = require("gem/Block")
var list = Block()
;[1,2,3].forEach(function(n) {
var text = "Hi "+n
var toggleButton = Button(text) // create a button
// make it do stuff when you click on it
toggleButton.on('click', function() {
if(toggleButton.text !== "RAWRR!!!") {
toggleButton.text = "RAWRR!!!"
toggleButton.state.set('color', 'rgb(128, 0, 0)')
} else {
toggleButton.text = text
toggleButton.state.set('color', 'black')
}
})
// add the button to the list
list.add(toggleButton)
})
var greet = Button("send", "Send your Greetings") // labels like 'send' can differentiate
// otherwise identical types of gems
list.add(greet)
// create styles with style objects ..
list.style = Style({
border: '1px solid blue', // .. that use familiar css values,
marginRight: 34, // .. camelCase css properties and integers interpreted
// as "px" values when appropriate,
Button: { // .. sub-gem styles,
$$firstChild: { // .. pseudo-class styles,
color: 'rgb(0,100,240)',
},
$state: function(state) { // .. more sophisticated styling techniques
return Style({
color: state.color
})
}
},
$send: { // .. style based on an object's label, and ..
color: 'green'
}
})
// append the list of buttons to the document body (so it shows up)
list.attach()
// custom gems (use your favorite javascript class library - here proto is being used)
var NameInput = proto(Gem, function() { // inherit from Gem
this.name = 'NameInput'
this.build = function(LabelText) { // the `build` method initializes the custom Gem
this.nameField = TextField()
this.add(Text(LabelText), this.nameField)
this.nameField.on('change', function() {
list.children[0].text = "Hi "+this.val
})
}
})
var nameInput = NameInput("Your Name: ")
greet.on('click', function() {
var text = Text("Whats up, "+nameInput.nameField.val+'?')
text.style = Style({display:'block'})
text.attach()
})
nameInput.attach()
If anything in the documentation is unclear, or you want to see more examples, the unit tests give a comprehensive and exhaustive set of examples to look at.
Gem.js?Gem objects) and Style objectsGem.js, you write in 100% javascript. The only html requirement is a document body. You can still add plain old HTML into your gems using gem.domNode.innerHTML tho if you so choose.Gems can be added as a child to any standard dom object and they can be styled with standard css stylesheets if you so choose.Gems give you direct access to their domNode so you can use the dom manipulation libraries you're used to.$state, $setup, and $kill javascript in your Style objects, you can include any javascript that is stylistic rather than structural.Gem modules with real APIs that anyone can release online. HTML snippets are so 1995.Gem.js works in modern browsers without polyfills.npm install gem
or download the built package Gem.umd.js from the 'dist' folder in the repository
var Gem = require('gem') // node.js and webpack
define(['Gem.umd.js'], function(gem) { ... } // amd
<script src="Gem.umd.js"></script>
<script>
Gem; // global 'Gem' module object
</script>
GemAll gems inherit from Gem - the basic building-block of the system. Gems are EventEmitters, and emitting events is one of the primary ways gems should communicate.
Gem is abstract and can't be instantiated on its own. See the section ''Custom Gems'' for details on how to create objects that inherit from Gem.
Gem.name - The name of the Gem. Used both for naming dom elements for view in browser dev tools and for styling.
Gem.attach(listOfGems) - Appends the passed gems to document.body. IMPORTANT: only attach a gem to the dom via
this attach function or a gem's attach/attachBefore method. Without this, styles won't be rendered.
Gem.attach(domNode, listOfGems) - Appends the passed gems to the passed domNode.
Gem.attachBefore(domNode, listOfGems) - Appends the passed gems before the passed domNode as a sibling.
Gem.detach(listOfGems) - Removes the passed gems from their respective dom parents.
Gem.createBody(callback) - Dynamically creates the body tag. Calls callback when done.
Gem.dev - (Default: false) - When set to true, certain debugging feature are enabled.
gem.parent - The Gem's parent (which will also be a Gem)
gem.children - An array of the Gem's children (which will all be Gems themselves).
gem.domNode - The Gem's standard dom node object.
gem.label - A string used for styling. Should be set once when the object is instantiated, and cannot change. See the section on Style objects for details about how this is used.
gem.excludeDomEvents - A set of dom events to exclude from automatic registration. Will have the structure {eventName1:1, eventName2:1, ...}. See the documentation for on for more details.
gem.state - An observer object that can be listened on for changes. Can be used for any purpose, but is intended for being used to create dynamically changing styles. See the section on Style objects for an example.
gem.add(gem, gem, ...) - Appends gems as children to the calling gem. This causes the domNodes of the passed gems to be appended to the calling gem's dom node.
gem.add(listOfGems) - Same as above, but listOfGems is an array of Gem objects.
gem.addAt(index, gem, gem, ...) - Adds gems as children to the calling gem at a particular index.
gem.addAt(index, listOfGems) - Same as above, but listOfGems is an array of Gem objects.
gem.addBefore(beforeChild, gem, gem, ...) - Adds gems as children to the calling gem before a particular child. If beforeChild is undefined, this will append the given nodes.
gem.addBefore(beforeChild, listOfGems) - Same as above, but listOfGems is an array of Gem objects.
gem.remove(gem, gem, ...) - Removes the passed gems as children.
gem.remove(listOfGems) - Same as above, but listOfGems is an array of Gem objects.
gem.remove(index, index, ...) - Removes, as children, the gems at the given indexes in the children list.
gem.remove(listOfIndexes) - Same as above, but listOfIndexes is an array of indexes to remove.
gem.attach(domNode=document.body) - Appends this Gem's domNode to the passed domNode (default document.body). IMPORTANT: only attach a gem to the dom via the attach function or a gem's attach/attachBefore method. Without this, styles won't be rendered.
gem.attachBefore(domNode=document.body) - Appends this Gem's domNode before the passed domNode (as a sibling).
gem.detach() - Removes this Gem's domNode from its dom parent.
gem.attr(attributeName) - Return the value of the attribute named attributeName on the Gem's domNode.
gem.attr(attributeName, value) - Sets the attribute to the passed value.
gem.attr(attributeObject) - Sets the attributes in the attributeObject, where attributeObject looks like: {attribute1: value1, attribute2: value2, ...}.
gem.style - Holds the object's Style object. Starts out undefined, and can be set to undefined to remove a Style that has been set. Changing this property triggers style affects in the Gem's children.
gem.visible - Setting this variable to false hides the gem using "display: none;". Setting this variable to true unhides it. Accessing the variable will return its visibility state.
gem.focus - Setting this variable to true gives the gem focus on the page. Setting this variable to false blurs it. Accessing the variable returns whether or not the gem is the focused element on the page.
gem.quiet.focus - Just like gem.focus but won't cause a "focus" or "blur" event.
gem.selectionRange - Returns an array representing the selection range in terms of visible character offsets. E.g. a value of [2,4] means that the current element has 2 visible entities (usually characters) selected within it at offset 2 and 4 from the start. Note that if there are hidden characters like multiple spaces in a row, or newlines, or other non-visible characters (mostly only applies to contenteditable nodes), they are ignored.
gem.selectionRange = [offsetStart, offsetEnd] - Setting the selectionRange property sets the selection inside the Gem's domNode based on the given offsets.
Example of selectionRange:
var x = Text("You're not my buddy, guy")
x.attach()
x.selectionRange = [0,6] // selects "You're"
Most of these are inherited from EventEmitter.
All methods and properties from EventEmitter are inherited by Gem. The important ones:
gem.emit(event, data, data2, ...) - Emits an event that triggers handlers setup via the Gem's on methods.
gem.on(event, callback) - Registers a callback that will be called when the passed event is emitted by the Gem. \
event - The string event name to listen for. If the passed event is one of the many standard dom events (e.g. 'click', 'mouseover', 'touchstart', etc), the passed handler will be registered as a dom event handler in one of three cases:
excludeDomEvents object is undefinedin the gem's excludeDomEvents propertycallback(data, data2, ...) - the callback gets any arguments passed to emit after the event name.gem.onCapture(event, callback) - Just like gem.on but listens on the capture phase of native browser events. Note: this doesn't currently listen on events that aren't native browser events.
gem.once(event, callback) - Like on but the callback will only be called the first time the event happens.
gem.off(event, callback) - Removes a callback as an event handler (the callback won't be called for that event again).
gem.removeListener(event,callback) - Same as off.
gem.removeAllListeners(event) - Removes all the callbacks for the passed event, except capture handlers.
gem.removeAllListeners() - Removes all callbacks except capture handlers.
gem.offCapture(event, callback) - Removes a capture handler.
ifonThe ifon and related methods are useful primarily for performance reasons. They allow registering event listeners only when they're needed, so that the browser doesn't get overloaded with event handlers. Its recommended that ifon is used whenever possible.
An example:
var text = Text("CLICK ME")
var parent = Block(text)
var handler;
parent.ifon('someoneClickedTheThing', function() {
text.on('click', handler = function() {
parent.emit('someoneClickedTheThing', "I can't believe it")
})
})
parent.ifoff('someoneClickedTheThing', function() {
text.off('click', handler)
})
gem.ifon(event, callback) - Registers a callback that will be called when a handler is registered for event if it had no handler registered previously. If there is already a listener attached to that event, callback is called immediately.
gem.ifon(callback) - Registers a callback that will be called when the first handler for any event is registered.
callback(event) - The callback gets the newly registered event type as its argument.gem.ifoff(event, callback) - Registers a callback that will be called when the last handler for event is unregistered.
gem.ifoff(callback) - Registers a callback that will be called when the last handler for any event is unregistered.
callback(event) - The callback gets the unregistered event type as its argument.gem.removeIfon() - Removes all ifon handlers.
gem.removeIfon(event) - Removes all ifon handlers for the passed event.
gem.removeIfon(callback) - Removes callback as an "all" ifon handler (a callback passed to ifon without an event).
gem.removeIfon(event, callback) - Removes callback as an ifon handler for the passed event.
gem.removeIfoff() - Removes all ifoff handlers.
gem.removeIfoff(event) - Removes all ifoff handlers for the passed event.
gem.removeIfoff(callback) - Removes callback as an "all" ifoff handler (a callback passed to ifoff without an event).
gem.removeIfoff(event, callback) - Removes callback as an ifoff handler for the passed event.
proxyThe proxy method uses ifon and ifoff to minmize the number of event listeners that need to be attached in the system.
gem.proxy(emitter, options) - Proxies event registration to emitter. \
emitter - The emitter (usually a Gem) to proxy handler binding to \options - An object that defines what events are proxied. If undefined, all events are proxied. The object can have one of the following properties:
only - An array of events to proxy.except - An array of events to not proxy. All other events are proxied.Example of proxy:
var A = Text()
var B = Text()
A.proxy(B)
A.on("click", function(x) {
console.log("hey hey heyyy! "+x)
})
B.emit("click", "Ughh..") // console prints "hey hey heyyy! Ughh.."
"attach" - Emitted when the gem is attached to the document.
"detach" - Emitted when the gem is detached from the document.
"newParent" - Emitted when a Gem gets a new parent. Note: this event is used by Style objects, so don't prevent these events.
"parentRemoved" - Emitted when a Gem is detached from its parent. Note: this event is used by Style objects, so don't prevent these events. \
Gem object will emit any standard dom event ("click", "mousedown", "keypress", etc) when listened on. Note that a Gem doesn't add an event listener to the dom node until someone listens on that event on the gem. This minimizes the number of event listeners that are registered on the page. To see the list of dom events this applies to (supposed to be all of them), see the top of src/node_modules/Gem.js
Gem.js is all about custom components. That's the point: your application should be built as a composition of custom gems on top of custom gems so that, instead of a million divs, you have semantically appropriate javascript web components.
In this documentation, we're going to be using the class library proto. The descriptions here apply to both inheriting from Gem and inheriting from any of the standard gems. There are a couple special properties to create when making a custom Gem:
name - The name is a required property, should be named whatever your class is named, and should be a somewhat unique name in your system (tho it isn't required to be unique).build() - The "sub-constructor". The constructor calls this method, passing all arguments, to the build method. The return value of build is ignored.defaultStyle - If set to a Style object, the style object will be the gem's default style. Unlike explicitly set Styles and inherited Styles, css properties in defaultStyle do cascade line-by-line. Also, if a gem inherits from another Gem class that also has a defaultStyle, the default styles mix together with the child Gem class style properties overriding the parent Gem class's default properties. So in the below example, if gem is given a style that defines color: green, it's fontWeight will still be 'bold'.For example:
var CustomGem = proto(Gem, function() {
this.name = "CustomGem"
this.defaultStyle = Style({
color: 'red',
fontWeight: 'bold'
})
this.build = function(x) {
this.x = x
}
})
var gem = CustomGem(5) // gem.x is 5
If you'd like to release a custom Gem or set of Gem objects, there are a couple of important things to remember to do:
Gem.js as a normal "dependency". Instead, it should be added as a "peerDependency" or perhaps a "devDependency". It shouldn't be a normal "dependency" because otherwise bundlers may bundle multiple copies of Gem.js when using your custom gem module (even though bundlers like webpack dedupe files, if the versions of webpack being used are slightly different, they would still package together both versions of Gem.js)<script> tag, do not bundle Gem.js in your distribution bundle. It should assume the gems global variable (e.g. gems.Gem) is available.protoIf you're building Gems with something other than proto (or are using a version of proto older than 1.0.17), note that Gem.js relies on the following properties:
proto sets this automatically, it is not a standard property and if you're using a different library from proto, you must set this manually.proto sets this appropriately, most class libraries probably don't and it isn't simple to manually set. See here for details.Also, make sure that Gem's constructor is called on new instances that inherit from Gem.
Properly subclassing a prototype in javascript isn't the simplest thing to do, but if you want to do it, here's how:
var CustomGem = function() {
Gem.init.call(this) // Gem's constructor must be called
}
CustomGem.parent = Gem // needed for correct Style rendering
var Intermediate = function(){}; Intermediate.prototype = Gem.prototype
CustomGem.prototype = new Intermediate()
CustomGem.prototype.name = 'CustomGem' // the name is a required property
CustomGem.prototype.constructor = CustomGem // required for correct Style rendering,
// and is a standard javascript convention
CustomGem.prototype.build = function(constructorArgument1, constructorArgument2, ...) {
// .. custom constructor code
}
CustomGem.prototype.customMethod = function() {
// ...
}
The built-in standard gems all inherit from Gem and so have all the methods and properties in the above documentation. For each build-in gem, its name property will be the same as the name the documentation uses for it. For example Button will have the name "Button".
To use these built in gems, access them via either require("gem/<GemName>") or Gem.<GemName>. For example:
var Table = require("gem/Table") // webpack or browserify
// or
var Table = Gem.Table // if loading the umd bundle in a <script> tag
There are some conventions that can help you learn to use standard Gems, and help make custom Gems you build more easily understood. These conventional properties, constructor parameters, and behavior are encouraged to be used in custom Gems built by you, especially if you're planning on open-sourcing them.
Every standard Gem has an optional first parameter label. This makes it easy and non-intrusive to label parts of your custom Gems for easy styling.
In as many cases as possible, Gems will use properties defined with getters and setters rather than using methods. There are a few standard properties that some gems have:
text - Gets and sets some static visual text that a Gem has. Button, Text, and Select.Option have this property.selected - Gets and sets the selected-state of the Gem. CheckBox, Select.Option, and Radio.Button have this property.val - Gets and sets some value that a gem has. This will never be the same as either text or selected. Radio, Select, TextArea, and TextField all have this property.quiet - Any gem that has a selected or val property will have a corresponding quiet.selected or quiet.val property that works in the same way, except that it doesn't emit any change events.This is a standard event that many gems can emit:
change - Emitted when an important value of a gem changes. This will always be either the gem's val property or its selected property (but never both). Change events won't have any information passed with them - you can access the object itself if you need data from it.Some gems have sub-gems specifically related to them. For example, Select has Option gems, and Table has Row and Header gems, and Row and Header have Cell gems respectively.
Select has an options map.Select or Table) to create a new sub-gem (e.g. Option or Row), append it to the calling gem, and returns that sub-gem. The method will be named the same as the sub-gem but in lower-case (e.g. selectGem.option(...) will return an Option gem).Your standard html <button>.
Button(text) - Returns a new button that has the passed text.
Button(label, text)
button.text - Sets or gets the button's text.
Your standard html <canvas>.
Canvas(height, width) - Returns a new Canvas object that has the passed dimensions.
Canvas(label, height, width)
canvas.height - Sets and gets the canvas's height.
canvas.width - Sets and gets the canvas's width.
canvas.context(type, attributes) - Returns a standard canvas context. The type and attribute parameters and return value are the same as the html-standard getContext.
canvas.toImg - Returns a data-url representing the image currently drawn on the canvas.
canvas.toDataURL - Same as canvas.toImg.
Your standard html <input type="checkbox">.
CheckBox() - Returns a new unchecked CheckBox.
CheckBox(label)
checkbox.selected - Sets and gets the checkbox's selected state (true for selected, false for unselected).
checkbox.quiet.selected - Same as selected but emits no change event.
A <div> that contains other gems.
Block(gem, gem, ...) - Returns a new container with all the passed gems as children (in the passed order).
Block(listOfGems) - Same as above except listOfGems is an array of gems.
Block(label, gem, gem, ...)
Block(label, listOfGems)
Your standard html <img>.
Image() - Returns a new empty image.
Image(imageSource) - Returns a new image with the passed imageSource.
Image(label, imageSource)
image.src - Gets or changes the image's source.
An <ol> or <ul> element.
List() - Returns a new empty list.
List(ordered) - Returns a new empty list. Is an ordered-list if ordered is true, and an unorderd-list otherwise.
List(listInit) - Returns a new populated list. listInit is an array containing either Gem objects or strings to add as list items.
List(ordered, listInit)
List(label)
List(label, ordered)
List(label, listInit)
List(label, ordered, listInit)
list.item(contents) - Creates a new ListItem with the passed contents and appends it to the list, which can either be a Gem or a string.
list.item(label, contents)
List.Item - The ListItem class.
List.Item(contents) - same as list.item above, except doesn't append the item to any list.
List.Item(label, contents)
Gem)A set of radio buttons. Radio itself is not a Gem, but rather contains a set of related RadioButtons (which are Gem objects).
Radio() - Returns a new Radio object where a button is not required to be set (same as Radio(false)).
Radio(required) - Returns a new Radio object. If required is true, a radio button will always be selected (and buttons cannot be deselected), otherwise radio-buttons can be deselected, and no radio button is selected by default.
radio.button(value) - Creates a new RadioButton with the passed string value that is a member of the Radio object.
radio.button(label, value)
radio.selectedOption - Returns the RadioButton object that is selected.
radio.val - Gets the value of the RadioButton that's selected, or selects the RadioButton that has the set value (e.g. radio.val = 'elvis' would select the radio button with the value "elvis")
radio.quiet.val - Same as val but emits no change event.
radio.remove(radioButton, radioButton, ...) - Removes the passed radio buttons from the Radio object's set. Note that this will not remove the buttons from the page - that must be done separately for whatever Gem contains the RadioButtons.
radio.remove(arrayOfRadioButtons) - Same as above, except the argument is an array of the RadioButtons to remove.
radio.remove(value, value, ...) - Removes the radio buttons that have the passed values from the Radio object's set.
radio.remove(arrayOfValues) - Same as above, except the argument is an array of the values who's radio buttons should be removed.
Radio.Button - The RadioButton class.
radioButton.val - Gets or sets the value of the radio button.
radioButton.selected - Gets whether the radio button is selected or not. If set to true, selects the button. If set to false, deselects it.
radio.quiet.val - Same as val but emits no change event.
radioButton.selectNext() - Sets the next radio button in the Radio object's set.
radioButton.selectPrevious() - Sets the previous radio button in the Radio object's set.
Your standard <select> element.
Select() - Returns a new empty selection list.
Select(selections) - Returns a new populated selection list.
Select(label, selections)
selections - An object with the structure {optionValue: optionText, ...}select.option(value, text) - Creates a new Option with the passed value and text, and appends it to the list.
select.option(label, value, text)
select.options - A map where each value is a Select.Option gem the Select instance contains, and each key is the value of that option.
select.val - Gets the value of the selected Option, or selects the Option with the set value (e.g. select.val = 'moo' selects the Option with the value 'moo').
select.quiet.val - Same as val but emits no change event.
Select.Option - The Option class.
Select.Option(value, text) - same as select.option above, except doesn't append the Option to any list.
Select.Option(label, contents)
option.selected - Gets or sets the selected state of the Option.
option.text - Gets or sets the display text of the Option.
option.val - Gets or sets the string value of the Option.
select.quiet.selected - Same as selected but emits no change event.
select.quiet.val - Same as val but emits no change event.
An <svg> element.
Svg(svgXml) - Returns a new Svg image using the passed svgXml. The svgXml must include the <svg> tag at the top-level.
Svg(label, svgXml)
Your standard <table> element.
Table() - Returns a new empty table.
Table(tableInit) - Returns a new populated table.
Table(label,tableInit)
tableInit - A list where each element in the list represents a row. Each element itself should be a list where each element is a Gem or string to put in a table Cell. E.g. Table([['a','b','c'],[Text('x'),Text('y')]]) is a table with two rows and three columns, where there are only two cells in the second row.table.row(rowInit) - Creates a new table TableRow (<tr>), and appends it to the table.
table.row(label, rowInit)
table.header(rowInit) - Creates a new table TableHeader (<th>), and appends it to the table.
table.header(label, rowInit)
rowInit - A list where each element is a Gem or string to put in a table TableCell. E.g. table.row(['a','b','c']) is a row with three cells.Table.Row - The TableRow class.
Table.Header - The TableHeader class.
Table.TableCell - The TableCell class.
Table.Row(rowInit) - same as table.row above, except doesn't append the TableRow to any table.
Table.Row(label, rowInit)
Table.Header(rowInit) - same as table.header above, except doesn't append the TableHeader to any table.
Table.Header(label, rowInit)
row.cell(contents) - Creates a new table TableCell (<td>) and appends it to the TableRow.
row.cell(label, contents)
header.cell(contents) - Creates a new table TableCell (<td>) and appends it to the TableHeader.
header.cell(label, contents)
contents - Either a string (text content) or any value you could pass into gem.add (a Gem, a list of Gems, etc).Table.Cell(contents) - Same as row.cell, but doesn't append the cell to any row.
Table.Cell(label, contents)
cell.colspan(columns) - Sets the column-span (colspan attribute) of the cell.
A <div> with text in it.
Text() - Returns an empty Text object.
Text(text) - Returns a Text object populated with the passed string text.
Text(label, text)
text.text - Sets or gets the object's text.
A multi-line text input field. Your standard <textarea> element.
TextArea() - Returns an empty TextArea.
TextArea(label)
textArea.val - Gets or sets the testArea's value (the text inside the text box).
textArea.quiet.val - Same as val but emits no change event.
A one-line text input field. Your standard <input type='text'> element.
TextField() - Returns an empty TextField.
TextField(password) - Returns an empty TextField with the password attribute, meaning any text inside the box will be displayed so that only the number of characters can be seen, and not the characters themselves.
TextField(label, password)
textField.val - Gets or sets the textField's value (the text inside the text box).
textArea.quiet.val - Same as val but emits no change event.
Style objects
If you're going to build a web application, why not do it with Style?
While a Gem is pretty analogous to its HTML node, Style objects in Gem.js are quite different from normal CSS.
In Gem.js, individual css style properties do not cascade. Instead, whole Style objects cascade. This may not seem like much of a difference, but it makes all the difference. For example:
var parentBlock = Block([
Text('a'),
Block([
Text('b'),
Text('c')
]),
List([Text('d')])
])
c.style = Style({
Text: { // 1
color: 'blue',
fontWeight: 'bold'
},
Block: {
Text: { // 2
color: 'red'
}
}
})
In the above example, "a" will be bold and blue, and "b" and "c" will be red. But "b" and "c" won't be bold - that property does not cascade. The Text styling inside Block is isolated from all previous stylings of Text, which means you don't have to worry about the styles someone used for elements further up the dom tree. I mentioned, tho, that whole Style objects do cascade, and that is why "d" will also be blue and bold even though it isn't a direct child of parentBlock.
Another difference is that Gem.js doesn't have selectors that can style any element on the page.
Traditional CSS stylesheets are developed by selecting a group of elements from the entire page
(via ids, classes, attributes, pseudoclasses representing element state, etc) and appending styles to them.
These styles may overwrite styles written earlier, and they themselves may be overwritten.
In Gem.js, Style objects can only be attached in a strict hierarchical setting, where only a specific section
of the dom can be affected. In the above example, the Text style marked 2 doesn't affect anything outside that inner Block.
For example, even though the text "d" is a Text object inside a Block object, it is not colored red.
That's because styles in Gem.js are not like the selectors you're used to from css.
They are strictly hierarchical - they only affect descendant Gem objects' (children, grandchildren, etc) from the point in
the dom they match.
The combination of the fact that Gem.js Style objects only cascade as a whole object and that styles are defined hierarchically makes styles modular and provides isolation from other styles on the page, so that it becomes much easier to understand and manage styling for a page or entire application.
Style constructorStyle(styleDefinition) - Creates a Style object.
styleDefinition is an object where key-value pairs can be either style properties or selectors:
<cssPropertyName>: the value is a valid css value for that style property.$setup: the value is a function to be run on a gem when the style is applied to it$kill: the value is a function to be run on a gem when a style is removed from it$state: the value is a function to be run when gem.state changes (ie when its change event fires).Style object or a nested styleDefinition object
<GemName>$<label>$$<pseudoclass>$inherit<cssPropertyName>This type of key-value pair is simple - just your basic css style. Example:
Style({
color: 'rgb(100, 200, 50)',
marginRight: 3
})
The above style would give a color and margin-right to whatever Gem is set with that style (gem.style = styleObject). Note that camelCase names can be used, and numbers are automatically appended with "px" if appropriate for the property (just like with jquery's css method).
$setup and $kill$setup(gem, style) - A function that is run when the style is applied to a gem. The passed style parameter is the style containing the $setup function.
$kill(gem, setupObject) - Run when the style is removed from a gem. Also gets the return value of the $setup function as its second argument.
For example:
var S = Style({
$setup: function(gem) {
gem.text = "I got zee style"
return 20
},
$kill: function(gem,setupValue) {
gem.text = "I'm "+setupValue+"% less cool"
}
})
var t = Text("x")
t.style = S
t.text === "I got zee style"
t.style = undefined
t.text === "I'm 20% less cool"
$state$state(state) is a function that is run when the gem's state observer property emits a change event (which happens when
its changed with its methods set, push, splice, or append). The state function is passed the value of gem.state.subject
as its parameter. The return value of the function should be a Style object to mix with the object's current style.
Note that if you create styles in $state functions, remember that you will create a new style every time the state changes. This may be a problem with some applications that have a lot of state changes, or particularly rapid state changes (its unclear at what point this could cause problems).
Example:
var c = Text("hi")
var colorStyles = {
yellow: Style({backgroundColor: 'yellow'}),
red: Style({backgroundColor: 'red'}),
green: Style({backgroundColor: 'green'})
}
c.style = Style({
color: 'blue',
$state: function(state) {
if(state.success) {
if(state.late) {
return colorStyles.yellow
} else {
return colorStyles.green
}
} else {
return colorStyles.red
}
}
})
c.state.set("success", true) // container's background turns green
c.state.set("late", true) // container's background turns yellow
In the above example, the container goes through all 3 backgroundColor colors as its state changes. In all states, the text color will be blue tho, since the $state style mixes with the primary style properties.
<GemName>This sets a style for the Gem with the given name. Only gems within the gem who's style this is are affected, gems that do not descend from the styled gem, and even the styled gem itself is not affected. For example:
var stylish = Style({
Text: {
color: 'red'
}
})
var container = Block([Text('a')])
var text = Text("b")
container.style = stylish
text.style = stylish
In the above example, only "a" is styled red. The Text "b" remains the default, black.
You can also give Gems a Style object, which is the same as the above form, except that the object-immediate is passed into the Style constructor:
var textStyle = Style({
color: 'red'
})
var stylish = Style({
Text: textStyle
})
Keep in mind that Gem styles are inherited by their parent in-full (not line-by-line like in css). So any Gem that isn't given its own explicit style inherits from its ancestors (if its ancestors have a style for that Gem). For example,
var a,b,c,d,e, dBlock
var tree = Block([
a = Text('a'),
Block([
b = Text('b'),
c = Text('c'),
dBlock = Block([
d = Text('d'),
Block([
e = Text('e')
])
])
])
])
tree.style = Style({
Text: {color: 'green'}
})
c.style = Style({
fontWeight: 'bold'
})
dBlock.style = Style({
Text: {textDecoration: 'underline'}
})
I hope you don't mind I assigned variables inside the Gem structure - don't worry, the structure would be the same if the variables weren't assigned, but assigning the variables allows me to manipulate them after the structure is defined.
In any case, in the above example, the tree object is given a style where Text gems are green. However, dBlock is given an alternate Text style.
How does that affect the resulting style? Well, "a" and "b" are colored green, but "d" and "e" are not green. Instead, "d" and "e" are the default color, black, and are underlined. This is because "d" and "e" inherit the Text style from dBlock which overrides the Text style given to tree.
And what about "c" you ask? Since "c" is given its own explicit style, that style also overrides any inheriting style. So "c" is bold and the default black.
$<label>Gem objects can be given a label property, which can be used to identify Gem objects of the same type that have different purposes within their parent.
This is essentially analogous to giving divs class names, and then styling using that class, except that it works in gem.js's hierarchical way of course. Note, tho, that a Gem can have only one label.
For example:
var container = Block([
Text("header", "Your Receipt, Sir: "),
Text("receipt", "1 bagel - $5, 3 buffulo - $45, 3 sticks dynamite - $100, 45 tons of wheat - $200")
Text("Thank you for using butler-copter!")
])
container.style = Style({
Text: {
fontWeight: 'bold',
color: 'blue'
},
$header: {color: 'gray'},
$receipt: {color: 'green'}
})
In the above example, the text "Your Receipt, Sir: " will be gray, the receipt text will be green, and the thank-you text
will be blue. Only the thank-you text will be bold.
Note that $label styles override gem styles, even if the gem style is "closer" to the gem. For example, in the following
example, the text "hi" will be gray, not blue.
var container = Block([
Block([
Text("hi")
])
])
container.style = Style({
$someLabel: {color: 'gray'},
Block: {
Text: {color: 'blue'}
}
})
$$<pseudoclass>Pseudoclasses filter out which Gem styles are given to. Also, the styles mix with the styles defined in the style-definition containing it. For example:
var x = Text("hi")
x.style = Style({
fontWeight: 'bold',
$$hover: {color: 'red'}
})
The above code changes the text from bold-black to bold-red when you hover over it, and back to black again when you move your mouse off the text.
Pseudoclasses also mix with each other when applicable. For example:
var container = Block([Text("a"), Text("b")])
container.style = Style({
Text: {
$$lastChild: 'bold',
$$hover: {color: 'red'}
}
})
In the above code, "a" will start black and change to red when you hover over it. "b" will start black and bold, but will change to red and bold when you hover over it.
To set a style only when multiple pseudoclasses apply, simply nest them. For example:
var text = Text("a")
text.style = Style({
$$lastChild: {
$$hover: {color: 'red'}
}
})
In the above code, "a" will turn red if it is both the last child of its parent and is hovered over.
Also, pseudoclasses may take parameters, which are passed in with parens like a javascript function. For example:
var c = Block([Text("a"),Text("b"),Text("c"),Text("d"),Text("e")])
c.style = Style({
Text: {
'$$nthChild(1+2n)': {color: 'red'},
}
})
In the above code, "a", "c", and "e" are red, while "b" and "d" are black (the default).
$inheritThe $inherit property, if set to true, indicates that the style inherits properties from the style "above" it - the
style that would be used if the current style wasn't there. For example in the following, the text inside the container gets a green background,
but also a red text color:
Style({
Text: {color: 'red'},
Block: {
Text: {
$inherit: true,
backgroundColor: 'green'
}
}
})
In the following, a Text gem with the label 'boom' would have both a green background and red text, whereas a Text gem without that label, would not have the background color:
Style({
Text: {color: 'red'},
$boom: {
$inherit: true,
backgroundColor: 'green'
}
})
Note that $inherit is ignored the top-level of psuedoclass styles, $state styles, and defaultStyles since they always inherit.
Style objects can be as simple as a few standard css properties, or can take the place of a whole css stylesheet and more. Here's an example of a more complex style:
var topBarHeight = 100
Style({
marginTop: topBarHeight,
Button: {
$setup: function(gem) {
var handler;
gem.on('moo', handler=function() {
console.log("He won't stop mooing!")
})
return {handler:handler}
},
$kill: function(gem, setupState) {
gem.off('moo',setupState.handler)
}
},
$closeButton: {
//future: $inherit: true, // inherits the Button style (if the gem is a Button)
position: 'absolute',
right: 3, top: 3,
width: 'calc(50% - 2px)'
},
Table: {
TableHeader: {
TableCell: {
borderBottom:'1px solid #000'
}
},
TableRow: {
'$$nthChild(1)':{
TableCell: {
borderTop: '1px solid #000'
}
},
TableCell: {
'$$nthChild(1)': {
borderLeft: "1px solid #000"
},
$$lastChild: {
borderRight: "1px solid #000"
}
},
$$lastChild: {
TableCell: {
borderBottom: "1px solid #000",
'$$nthChild(1)': {
borderLeft: "1px solid #000",
},
$$lastChild:{
borderRight: "1px solid #000",
}
}
}
}
},
TopBar: {
marginTop: -topBarHeight+2,
position: 'absolute',
right: 0,
Search: {
position: 'relative',
top: -3,
$field:{
height: 23
}
},
DropTab: {
position: 'static',
$wrapper: {
position: 'static'
},
$menu: {
position: 'absolute',
border: border,
marginTop: 1,
backgroundColor: 'white',
cursor: 'pointer',
Text: {
color: 'bonkers'
}
},
$button: {
border: border,
fontSize: 24,
fontWeight: 'bold'
}
},
$userDropTab: {
//future: $inherit: true, inherits from DropTab above
cursor: 'pointer'
},
}
})
styleObject.mixstyleObject.mix(styleObject2)
styleObject.mix(styleDefinition)
styleObject.mix(styleObject2, mixInherit)
styleObject.mix(styleDefinition, mixInherit)
Returns a new style that combines together calling style object and the passed style object or style definition. The properties from the passed style object override the ones from the calling object.
Examples:
var newStyle = oldStyle.mix({
color: 'red'
})
var newStyle2 = oldStyle.mix(anotherStyle)
styleObject.copy()Returns a new style that is a copy of the calling style object but has a new className. This was written mainly for internal use.
Style.addPseudoClassStyle.addPseudoClass(name, options) - Creates a new pseudoclass that can be used in Style objects. This can be used to create all-new psuedoclasses no one's ever thought of before!
name - The name of the new pseudoclassoptions - An object with the members:
check(gem, processedParameter) - A function that returns true if the pseudoclass applies to passed gemsetup(gem, startCallback, endCallback, processedParameter) - A function that should call startCallback() when the pseudoclass starts applying, and endCallback() when it stops applying. Can return a state object that will be passed to the kill function.
processedParameter - The parameter passed to the pseudoclass (e.g. in ":not(:first-child)", ":first-child" is the parameter). If a processParameter function is given, this will be the return value of that function.kill(gem, state) - A function that cleans up any event listeners or anything else set up in the setup function.emulated - (Optional - default false) Set to true if this implements a native pseudoclass. If true, Gems will attempt optimize the pseudoclass using native css if possible.processParameter(parameter) - (Optional) Takes the pseudoclass parameter and returns some object representing it that will be used by the setup and check functions.parameterTransform(parameter) - (Optional) Returns a modified version of the passed parameter that will be used in place of the given parameter in native-rendered psuedoclass styles. This is useful in cases where native pseudoclass parameter parsing is unnecessarily strict (eg. nth-child parameters)styleObject.toStringstyleObject.toString() - Outputs a serialized representation of the style as a string. Note that $state, $setup, and $kill functions are serialized by using their function's toString method.
Style.fromStringStyle.fromString(styleString, context) - Converts styleString into a Style object.
styleString - Should have originally been output from styleObject.toString()context - An object where each key is a variable name that will be available in any $state, $setup, or $kill functions, and each value is the value that variable will have. Note that the variable Style is already defined for you if you don't specify it in the context.styleObject.toObjectstyleObject.toObject() - Outputs a regular javascript object representing the Style object. If passed back into the Style constructor, will render the same style.
Any pseudoclass that exists in standard css can be used by gem.js, even if it isn't build-in with a js-rendered emulation. The catch is that their use is limited. The following things aren't supported for these:
$setup, $kill, or $state functions within the pseudoclass style definitionhover - The usual :hover pseudoclasschecked - The usual :checked pseudoclassrequired - The usual :required pseudoclasslastChild - The usual :last-child pseudoclassnthChild(a+bn) - The usual :nth-child pseudoclass (with more tolerant parameter parsing)Note that, while the list of built-in pseudoclasses is currently short, all standard pseudoclasses can be defined except the ":visited" pseudoclass, because the necessary information is not available via javascript (a browser "security" policy).
Gem.js unifies the default styles of dom nodes - all objects that inherit directly from Gem have the same default styling unless they define their defaultStyle property.
The base default is mostly the same as css's base default. The two defaults that are different for Gem objects:
display - "inline-block"position - "relative"box-sizing - "border-box" (excepting <img> nodes, which are still defaulted to content-box because pixel perfect image sizing is often important)Also, while most css styles are not inherited from a Gem's parent, the following are inherited:
colorcursorfontFamilyfontSizefontStylefontVariantfontWeightvisibilityAnd while gem.js generally rejects css's use of cascading, there is some similar cascading going on, but much more simplified and localized. Defining this behavior in terms of "cascading order" (where later additions override earlier), the order is:
defaultStyle property of the gem instance's furthest ancestor classdefaultStyles in the Gem's ancestry)defaultStyle property of the Gem's parent classdefaultStyle property of the Gem itselfstyle property)Often in traditional web development, all the HTML will be rendered and any javascript for them initialized on page load, and the elements that shouldn't be shown to the user are simply hidden, and then shown when needed. Using gem.js, its recommended that you create and remove nodes as needed, rather than showing and hiding (using visible). The only reason to use the show/hide technique is if the element in question is particularly expensive to generate.
Here's a list of other available Gem modules:
Gem.label is not dynamic (can't be changed) because it is intended to be used to identify a particular Gem when multiple Gems of the same type are used alongside eachother. If you're looking for a way to change styles dynamically, use Gem.state.Gem.js is notGem.js is not:
Improve error messages for styles
consider adding vertical-align:top to the default css, since it solves weird issues with inline-blocks causing extra bottom-margin: http://stackoverflow.com/questions/20310690/overflowhidden-on-inline-block-adds-height-to-parent
Emulate the :not psuedoclass
Figure out how to support animations, @keyframes and that kind of thing
support css animations
var animation = Style.Animation({
name: 'slidein' // produces a css style like __defaultName__2_slidein
// to prevent name collisions
from: {
margin-left: 100%,
width: 300%
},
'75%': {
width: '200%'
},
to: someStyleObject
})
Style({
anim: animation, // anim cause its short and animation
// is already taken by plain css
animationDuration: 300 // milliseconds
})
Maybe if a gem has an explicit style set, it ignore's any styling from its parent (ie the componentStyleMap)
user-defined style properties
Finish MultiSelect (currently may not fire certain events with certain ways of selecting things with the mouse)
Make all controls usable via the keybaord
Consider making Style objects dynamically changable, and also inheritable/extendable so that you can extend the style object of a Gem instead of having to extend the object passed to a Style prototype
in separate module (a Gems utility kit or something):
Optimization ideas:
selected and val propertiesradio.selected to radio.selectedOption (deprecating radio.selected but leaving it in place)attachBeforestyleObject.toString, Style.fromString, and styleObject.toObjectmixInherit paramter for Style.mix to default to true, and documenting that parametergem now that I have access to that nameaddAt method and .style setter by between 10 and 30 times by
gem.attach method and Gems.attach function to take an optional first parameter - a domNode to append to in place of document.body
Gems.attach function can no longer take varargs of gems (eg Gems.attach(gem1, gem2, gem3) - instead do Gems.attach([gem1, gem2, gem3]))attach function or method. Without this, styles won't be rendered.processParameter in addPseudoClass optional like the docs sayStyle objects (that use any Style feature)
* Optimizing pseudoclass styles when their style branch can be rendered in pure-css
* defaultStyle styles can be arbitrary Style objects now
* $state styles can be arbitrary Style objects now
* $label changed from being a modifier on a Gem style to indicating a whole new labeled gem style (see section on $label for details)
* augmenting nth-child to be able to be more sane in how it processes its input (you can reverse the order of the terms and whitespace is tolerated)
* changing the default of box-sizing to 'border-box' except for images, which retain the 'content-box' defaultundefined is passed as a style, it is now ignored
* fixing bug: an array of gems couldn't be passed to table.cellifon and ifoff for proxying browser events through Gems
* Override the on method so that standard browser events are automatically attached to domNodes
* provide a way to exclude certain events, so they can be set up in an alternate wayifon and ifoff methodsWant to contribute? Start with the Contributing Guide!
Anything helps:
Released under the MIT license: http://opensource.org/licenses/MIT
FAQs
A view library for building and styling web components in pure-javascript.
The npm package gem receives a total of 382 weekly downloads. As such, gem popularity was classified as not popular.
We found that gem demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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