Dynamic style sheets for web components.
Why do we need transpilers like sass or stylus when we can use javascript to do the same and much more?
By leveraging namespaces we can solve the cascading problem better than bem and make our components truly reusable and composable.
Access css declarations and values from js without DOM round trip.
Smaller footprint because of code reuse and no vendor specific declarations
Take a look at examples directory.
Syntactic differences compared to CSS
Jss styles are just plain javascript objects. They map 1:1 to css rules, except of those modified by plugins.
{
'.carousel-caption': {
'position': 'absolute',
'z-index': '10',
},
'hr': {
'border': '0',
'border-top': '1px solid #eee'
},
'@media (min-width: 768px)': {
'.modal-dialog': {
'width': '600px',
'margin': '30px auto'
},
'.modal-content': {
'box-shadow': '0 5px 15px rgba(0, 0, 0, .5)'
},
'.modal-sm': {
'width': '300px'
}
}
}
Multiple declarations with identical property names
I recommend to not to use this if you use jss on the client. Instead you should write a function, which makes a test for this feature support and generates just one final declaration.
In case you are using jss as a server side precompiler, you might want to have more than one property with identical name. This is not possible in js, but you can use an array.
{
'.container': {
background: [
'red',
'-moz-linear-gradient(left, red 0%, green 100%)',
'-webkit-linear-gradient(left, red 0%, green 100%)',
'-o-linear-gradient(left, red 0%, green 100%)',
'-ms-linear-gradient(left, red 0%, green 100%)',
'linear-gradient(to right, red 0%, green 100%)'
]
}
}
.container {
background: red;
background: -moz-linear-gradient(left, red 0%, green 100%);
background: -webkit-linear-gradient(left, red 0%, green 100%);
background: -o-linear-gradient(left, red 0%, green 100%);
background: -ms-linear-gradient(left, red 0%, green 100%);
background: linear-gradient(to right, red 0%, green 100%);
}
API
Access the jss namespace
var jss = window.jss
var jss = require('jss')
Create style sheet
jss.createStyleSheet([rules], [named], [attributes])
rules
is an object, where keys are selectors if named
is not truenamed
rules keys are not used as selectors, but as names, will cause auto generated class names and selectors. It will also make class names accessible via styleSheet.classes
.attributes
allows to set any attributes on style element.
var styleSheet = jss.createStyleSheet({
'.selector': {
width: '100px'
}
}, {media: 'print'}).attach()
<style media="print">
.selector {
width: 100px;
}
</style>
Create namespaced style sheet.
Create a style sheet with namespaced rules. For this set second parameter to true
.
var styleSheet = jss.createStyleSheet({
myButton: {
width: '100px',
height: '100px'
}
}, true).attach()
console.log(styleSheet.classes.myButton)
<style>
.jss-0 {
width: 100px;
height: 100px;
}
</style>
Attach style sheet
styleSheet.attach()
Insert style sheet into render tree.
styleSheet.attach()
Detach style sheet
styleSheet.detach()
Remove style sheet from render tree to increase runtime performance.
styleSheet.detach()
Add a rule
styleSheet.addRule([selector], rule)
Returns an array of rules, because you might have a nested rule in your style.
You might want to add rules dynamically.
var rules = styleSheet.addRule('.my-button', {
padding: '20px',
background: 'blue'
})
Add rule with generated class name.
var rules = styleSheet.addRule({
padding: '20px',
background: 'blue'
})
document.body.innerHTML = '<button class="' + rules[0].className + '">Button</button>'
Get a rule
styleSheet.getRule(selector)
var rule = styleSheet.getRule('.my-button')
var rule = styleSheet.getRule('myButton')
Add a rules
styleSheet.addRules(rules)
Add a list of rules.
styleSheet.addRules({
'.my-button': {
float: 'left',
},
'.something': {
display: 'none'
}
})
Create a rule without a style sheet.
jss.createRule([selector], rule)
var rule = jss.createRule({
padding: '20px',
background: 'blue'
})
$('.container').css(rule.style)
Register plugin.
jss.use(fn)
Passed function will be invoked with Rule instance. Take a look at plugins like extend
, nested
or vendorPrefixer
.
jss.use(function(rule) {
})
Plugins
Things you know from stylus like @extend, nested selectors, vendor prefixer are separate plugins.
Full list of available plugins
Install
npm install jss
bower install jsstyles
Convert CSS to JSS
jss
jss source.css -p > source.jss
Benchmarks
To make some realistic assumptions about performance overhead, I have converted bootstraps css to jss. In bench/bootstrap
folder you will find jss and css files. You need to try more than once to have some average value.
In my tests overhead is 10-15ms.
Run tests
Locally
npm i
open test/local.html
From github
Tests
License
MIT