Using Libraries that Expect jQuery to be Global

Some legacy JavaScript applications use programming practices that don't play well with the new practices promoted by Webpack. The most common of these problems is using code (e.g. jQuery plugins) that assume that jQuery is already available via the $ or jQuery global variables. If those variables are not defined, you'll get these errors:

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Uncaught ReferenceError: $ is not defined at [...]
Uncaught ReferenceError: jQuery is not defined at [...]

Instead of rewriting everything, Encore allows for a different solution. Thanks to the autoProvidejQuery() method, whenever a JavaScript file uses the $ or jQuery variables, Webpack automatically requires jquery and creates those variables for you.

So, when working with legacy applications, you may need to add the following to webpack.config.js:

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Encore
    // ...
+     .autoProvidejQuery()
;

Internally, this autoProvidejQuery() method calls the autoProvideVariables() method from Encore. In practice, it's equivalent to doing:

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Encore
    // you can use this method to provide other common global variables,
    // such as '_' for the 'underscore' library
    .autoProvideVariables({
        $: 'jquery',
        jQuery: 'jquery',
        'window.jQuery': 'jquery',
    })
    // ...
;

Accessing jQuery from outside of Webpack JavaScript Files

If you also need to provide access to $ and jQuery variables outside of JavaScript files processed by Webpack (e.g. JavaScript that still lives in your templates), you need to manually set these as global variables in some JavaScript file that is loaded before your legacy code.

For example, you could define a common.js file that's processed by Webpack and loaded on every page with the following content:

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// require jQuery normally
const $ = require('jquery');

// create global $ and jQuery variables
global.$ = global.jQuery = $;