@pelagiccreatures/sargasso

@PelagicCreatures/Sargasso

Simple, Fast, Supervised Javascript Controllers for HTML Elements.

Demo Site

HTML elements sometimes need a nervous system to see and respond to what's going on around them - Sargasso element controllers are fully aware of their environment.

Events such as Document (DOM) insertions and deletions, HIJAX Page load, Scrolling, Resizing, Orientation and messages from Managed Web Workers are passed to Sargasso controllers allowing them to efficiently implement any behavior they need to perform.

@author Michael Rhodes (except where noted)
@license MIT
Made in Barbados 🇧🇧

This is a very lightweight, pure ES6 framework (with only few dependencies) which aims to use the most advanced stable features of modern browsers to maximum effect leaving the historical cruft, kludges and code barnacles infesting older web frameworks behind. The result is lean, highly performant and clean code that simplifies the complex technologies behind modern progressive web apps and web sites.

HIJAX made easy - this framework implements an asynchronous page loading scheme which supports deep linking and lightning fast page loads where only dynamic content areas are merged between pages leaving css, js, web workers and wrapper elements intact. Sargasso controller instances are managed as needed when their element appears in the DOM and destroyed when their element is removed.

Performance is optimized using shared event listening services which are fully debounced during large updates. Services are provided to schedule content changes using the browser's animation frame event loop and computation heavy tasks can be easily offloaded to managed web workers resulting in highly performant pages.

npm install @pelagiccreatures/sargasso

Bootstrap Sargasso:

The ES and the CommonJS bundles both expose:

• Sargasso - the sargasso super class
• registerSargassoClass - function to register your sub classes
• bootSargasso - start sargasso services and HIHAX

Most browsers are aware of ES6 and modules these days but but you can use the module/nomodule scheme to fall back to the common js bundle if needed.

<script type="module">
	import from "https://cdn.jsdelivr.net/npm/@pelagiccreatures/sargasso/dist/sargasso.es.js"
	... your code here ...
</script>

// optional - deal with the antiques if yo see fit.
<script src="https://cdn.jsdelivr.net/npm/@pelagiccreatures/sargasso/dist/sargasso.common.js" nomodule></script>
<script nomodule defer>
	... your code here ...
</script>

In production you probably want to host the bundles yourself instead of using the CDN and probably even make your own bundles including your subclasses using webpack or rollup or something.

For the '... your code here ...' part, it's the same in both cases. You need to at least start up the services.

<script>

	let options = {
		hijax: {
			onError: (level, message) => { alert('Something went wrong. ' + message) }
		}
	}

	// boot supervisors and HIJAX loader
	window.loadPageHandler = bootSargasso(options)

	// define a custom class and register the classname.
	class MyClass extends Sargasso {} // This won't do very much...
	registerSargassoClass('MyClass',MyClass)

</script>

Adding Your Sargasso class to an HTML element

Sargasso watches the DOM for any elements tagged with the data-sargasso-class attribute and instantiates the Sargasso class specified while hooking up the appropriate services. When the underlying element is removed from the DOM (loading a new page or something) it automatically destroys any dangling Sargasso objects.

<div data-sargasso-class="MyClass">This element has a MyClass Sargasso controller</div>

You can also defer the instantiation using the lazy method by tagging it with data-lazy-sargasso-class instead of data-sargasso-class which will only start up the class when the element is visible in the viewport

HIJAX

Sargasso automatically captures <a href=".."> tags and calls the LoadPageHandler instead of letting the browser load pages. You can make a link be ignored by hijax by setting the <a href=".." data-no-hijax>. Offsite links and links with targets are automatically ignored. bootSargasso also returns the function LoadPageHandler(href). You must call this to load a new page programatically.

EG. instead of location.href= '/home', use LoadPageHandler('/home')

Mark dynamic content

New pages are loaded via AJAX and are merged with the current page only replacing elements marked with data-hijax from the new page.

<html>
	<head>
	</head>
	<body>
		static stuff

		<div id="page-body" data-hijax>
			<p>this changes from page to page</p>
			<div>lots of html here</div>
		</div>

		more static stuff

		<div id="some-element" data-hijax>
			<p>this also changes from page to page</p>
		</div>

		more static stuff
	</body>
<html>

Note that data-hijax elements must have well formed child html elements. Not like this: <div>I'm just text. No child elements. Won't work.</div>

Sargasso Object Lifecycle

When the object is instantiated, the supervisor will call the start() method of the object. Beyond responding to scrolling, resize and other responsive events, you will probably want to interact with your element in some way. You should use this hook to set up any element events you need to respond to such as clicking a button, responding to touch events or key presses, etc.

Defining SubClasses:

Your Sargasso subclasses subscribe to event feeds to be notified of events.

Methods to override as needed: don't forget to call super.xxx() in your subclass

method	description
constructor(element, options = {})	subscribe to services by setting options properties. All default to false so only set the ones you need watchDOM, watchScroll, watchResize, watchOrientation, watchViewport {xxx:true}
start()	set up any interactions and event handlers
sleep()	remove any event handlers defined in start() and cleanup references
DOMChanged()	called if options 'watchDOM: true' when DOM changes
didScroll()	called if options 'watchScroll: true' when scroll occurs
didResize()	called if options 'watchResize: true' when resize changes
enterViewport()	called if options 'watchViewport: true' when element is entering viewport
exitViewport()	called if options 'watchViewport: true' when element is exiting viewport
enterFullscreen()	called if options 'watchOrientation: true' when user rotates phone or if setFullscreen is called
exitFullscreen()	called on exit fullscreen
newPage(old, new)	on a new page
didBreakpoint()	new screen width breakpoint
elementEvent(e)	this.element received an 'sargasso' event
workerOnMessage (id, e)	id is the worker sending the message. Any payload from the worker postMessage is in e.data.xxx as defined by the worker

Properties

property	description
this.element	the element we are controlling

Utility Methods:

method	description
hasClass('cssclass')	returns true if this.element has cssclass
addClass('cssclass')	add cssclass to this.element
removeClass('cssclass')	remove cssclass to this.element
css({})	set css pairs defined in object on this.element
scrollTop(newTop)	get and set the current scroll position
queueFrame(function)	queue a function to execute that changes the DOM
workerStart(id, codeOrURL)	start a web worker with id. Ignored if worker id already installed (see lib/LazyBackground.js for a shared worker example)

You need to let sargasso know about your class: registerSargassoClass('MyClass', MyClass)

Using Animation Frames

To avoid any chaotic repaints you should only make DOM changes inside animation frames - don't do any long processes in the responsive callbacks or things might bog down the browser UI.

class MyButtonClass extends Sargasso {

	constructor(element, options = {}) {
		options.watchViewport = true // tell me when I am visible
		super(element, options) // important!
	}

	// listen for click
	start() {
		super.start() // important!
		this.clicker = (e) => {
			this.clicked()
		}
		this.element.addEventListener('click', this.clicker, false)
	}

	// cleanup listener
	sleep() {
		this.element.removeEventListener('click', this.clicker)
		super.sleep() // important!
	}

	// use an animation frame to mutate the DOM
	clicked() {
		let frame = () { // set up a DOM mutation
			this.addClass('clicked')
		}
		this.queueFrame(frame) // schedule it
	}

	enterViewport() {
		// do some stuff such as modify element html or classes
		let frame = () => {
			this.element.innerHTML = '<p>Hello viewport! Please click me!'
		}
		this.queueFrame(frame)
	}
}

Then in HTML:

<style>
	.clicked { background-color:red; }
</style>

<button data-sargasso-class="MyButtonClass">Click me and I'll turn red!</button>

Using managed Web Workers

You should offload compute heavy tasks to a new thread when possible.

Sargasso controllers have build in managed Web Workers that can be defined in external scripts or inline code blobs simplifying the management of running workers.

The worker code runs when it receives an onmessage event

A web worker, once installed, could be used by many instances so sargasso sets e.data.uid to the id on the instance that is invoking the worker which we need to pass back in the postMessage so we know who is who.

class MySubClass extends Sargasso {

	...

	someMethod() {

		/*
			myWorker can be the url of a worker script or
			inline code as in this example
		*/

		let pointlessMath = `onmessage = function (e) {
			const baseNumber = e.data.power
			let result = 0
			for (var i = Math.pow(baseNumber, 7); i >= 0; i--) {
				result += Math.atan(i) * Math.tan(i)
			};
			postMessage({
				uid: e.data.uid, // Important! always pass this back in the message
				result: 'Done doing pointless math: ' + result
			})
		}`

		// create the worker to be managed by sargasso and give it an id
		// the id can be unique to your task or shared by many sargasso
		// controller
		this.workerStart('pointlessMath', pointlessMath)

		let data = { power: 12 }
		this.workerPostMessage('pointlessMath', data) // send message to the worker
	}

	// listen for worker result
	workerOnMessage (id, e) {
		if (id === 'pointlessMath') {
			const frame = () => {
				this.element.innerHTML = e.data
			}
			this.queueFrame(frame)
		}
		super.workerOnMessage(id, e)
	}
}

Viewing the Test Page in the example directory

To use Hijax you have to serve the files (window.popstate can't deal with file://...) so run SimpleHTTPServer in the project example directory to see demo page

python -m localhost.py

then point your browser to http://localhost:8000/index.html