Create custom js and including third-party library

Create theme.js

1. Create theme.js within the theme directory <Vendor>/<theme>/web/js/theme.js with this content:

define([
  "jquery"
], 
function($) {
  "use strict";

  // Here your custom code...

});

2. Declare theme.js with a requirejs-config.js file

Create a requirejs-config.js file within the theme directory: <Vendor>/<theme><theme>/requirejs-config.js with this content:

var config = {

  // When load 'requirejs' always load the following files also
  deps: [
    "js/theme"
  ]

};

js/theme is the path to our custom theme.js. The .js extension is not required.

Custom requirejs-config.js will be merged with other requirejs-config.js defined in Magento.

RequireJS will load our theme.js file, on each page, resolving dependencies and loading files in an async way.

Optional: Including third-party library

1. Add the library in web/js: <Vendor>/<theme>/web/js/vendor/jquery/library.js
2. Open requirejs-config.js and add this content:

var config = {

  deps: [
    "js/theme"
  ],

  // Paths defines associations from library name (used to include the library,
  // for example when using "define") and the library file path.
  paths: {
    'library': 'js/vendor/jquery/library',
  },

  // Shim: when you're loading your dependencies, requirejs loads them all
  // concurrently. You need to set up a shim to tell requirejs that the library
  // (e.g. a jQuery plugin) depends on another already being loaded (e.g. depends
  // from jQuery).
  // Exports: if the library it's not AMD aware, you need to tell requirejs what 
  // to look to know the script loaded correctly. You can do this with an 
  // "exports" entry in your shim. The value must be a variable defined within
  // the library.
  shim: {
    'library': {
      deps: ['jquery'],
      exports: 'jQuery.fn.library',
    }
  }

};

3. Add the dependency within theme.js:

define([
  'jquery',
  'library'
], 
function($) {

  // ...

});

Your theme directory structure now

app/design/<area>/<Vendor>/<theme>/
├── web/
│ ├── css/
│ │ ├── source/ 
│ ├── fonts/
│ ├── images/
│ ├── js/
│ │ ├── theme.js
│ │ ├── vendor/
│ │ │ ├── jquery/
│ │ │ │ ├── library.js

Links:

• Create custom theme
• Styles

Resource:

• Create cusom js and include third-party library