@degjs/module-loader

moduleLoader

Whenever possible, it's best to bundle modules during development. However, in certain situations (such as a restrictive CMS, or when loading JavaScript after a specific user interaction), it may be necessary to load a module asynchronously at runtime.

The moduleLoader module does exactly that, either on page load or on demand via an HTML attribute.

Install

moduleLoader is an ES6 module. Consequently, you may need a transpiler (Babel is a nice one) to compile moduleLoader into compatible Javascript for your runtime environment.

If you're using NPM, you can install moduleLoader with the following command:

$ npm install @degjs/module-loader

Usage

Regardless of whether you load modules on page load or on demand, you must set the data-module attribute on your HTML elements:

<div class="my-components my-component-1" data-module="components/myComponent1">
    Component 1
</div>

<div class="my-components my-component-2" data-module="components/myComponent2">
    Component 2
</div>

Option A: Load modules on page load

import moduleLoader from "@degjs/module-loader";

moduleLoader();

Option B: Load modules on demand

moduleLoader uses the MutationObserver API to watch for elements with data-module attributes that are added to the DOM by JavaScript after the page is loaded.

import moduleLoader from "@degjs/module-loader";

moduleLoader();

document.body.insertAdjacentHTML('beforeend', `
    <div class="my-components my-component-3" data-module="components/myComponent3">
        Component 3
    </div>
`);

Upon each successful load, an object is passed to the loaded module containing the following values:

• containerElement: The element from which the module was called.

Options

options.moduleDataAttr

Type: String
The name of the data attribute that defines the module to be loaded.
Default: data-module

options.elToObserve

Type: Element
The DOM element to observe for dynamically added elements.
Default: document.body

options.enableObservation

Type: Boolean
In some cases, you may know that no elements with modules will be added to the page after page load. Setting to false disables the potentially expensive mutation observer.
Default: true

options.loadingMethod

Type: String
By default, moduleLoader will attempt to load native JavaScript modules using the import() method, but will automatically fall back to SystemJS's System.import() method in unsupported browsers. This behavior can be overridden with this setting. Options: auto, system, esm Default: auto

options.basePath

Type: String
The base path of the JS module. This can be overridden at the element level by adding a data-basepath attribute to the element. Default: /js/

options.filenameSuffix

Type: String
The suffix of the JS bundle being loaded in browsers that support modules. This can be overridden at the element level by adding a data-suffix attribute to the element. Default: -bundle.js

options.filenameNoModuleSuffix

Type: String
The suffix of the JS bundle being loaded in browsers that don't support modules. This can be overridden at the element level by adding a data-no-module-suffix attribute to the element. Default: -bundle-nomodule.js

Browser Support

moduleLoader depends on the following browser APIs:

• MutationObserver: Documentation | Polyfill (Note: moduleLoader 4.0.2+ will work in IE10 without a polyfill, but dynamic module loading after the DOM is loaded will not. For IE10, either polyfill or use moduleLoader 3.0.1)

To support legacy browsers, you'll need to include polyfills for the above APIs.