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ember-m-js-loader

This Ember.js addon helps load the js file(s) on demand, i.e. lazy loading, inside the <script> tag in the document <body> using the service m-js-loader .

Compatibility

Ember@^3.0.0

Deferred Loading of JS

The ambitious SPAs need more than one JS resources (external libraries) and some of these JS resources can be more functionality centric and may not be required to get loaded on the initial screen or may be required only for few of screens. The loading of scripts that are not necessary for the initial page load can be deferred until after the initial load. Doing so can help reduce resource contention and improve performance.

Suppose a web app uses Maps Library (like leaflet) for displaying maps, which comes with its own JS. The maps are displayed only on couple of routes other than home screen. So the home screen is not needed to load the JS for maps. The maps JS should be loaded when the routes displaying maps are requested. In this scenario, its always preferable to load the JS dynamically.

.load(attr)

The method to load a JS file on demand.

attr is a JSON object which holds the attribute values for the <script> tag to load JS. It should at least have src property set to the source of the JS.

mJsLoader: Ember.inject.service('m-js-loader'), 
beforeModel() {
    this.get('mJsLoader').load({
            src: 'http://cdn-assets/maps.js',
            integrity: 'sha384-shfssiufhnof7348f738f7bw8g+Pmsjshdinwe98',
            crossorigin: 'anonymous'
        });
}

Promise Based Load

The service m-js-loader returns a promise. The service listens to the events onload and onerror on the <script> tag in which the JS is loaded. It resolves the promise inside onload event and rejects it if onerror event is raised.

Use of this promise is completely optional and upto the requirement of the app. If a route needs to wait until the JS gets loaded then the service can be used inside the beforeModel hook.

mJsLoader: Ember.inject.service('m-js-loader'), 
beforeModel() {
	return this.get('mJsLoader').load({
		src: '/assets/maps.js'
	});
}

Caching

The service m-js-loader caches the srcs loaded to avoid injecting the same JS more than once.

CORS

The service inserts a <script> tag which as good as having it hardcoded at the time of html load. So no CORS issue.

Installation

ember install ember-m-js-loader

Usage

[Longer description of how to use the addon in apps.]

Contributing

Installation

  • git clone <repository-url>
  • cd ember-m-js-loader
  • npm install

Linting

  • npm run lint:js
  • npm run lint:js -- --fix

Running tests

  • ember test – Runs the test suite on the current Ember version
  • ember test --server – Runs the test suite in "watch mode"
  • npm test – Runs ember try:each to test your addon against multiple Ember versions

Running the dummy application

For more information on using ember-cli, visit https://ember-cli.com/.

License

This project is licensed under the MIT License.