Attention

TYPO3 v8 has reached its end-of-life March 31st, 2020 and is not maintained by the community anymore.

You can order Extended Long Term Support (ELTS) here: TYPO3 ELTS.

Dependency Handling¶

Let us try to explain the dependency handling with the most used JS lib: jQuery

To prevent the "$ is undefined" error, you should use the dependency handling of RequireJS. To get jQuery working in your code, use the following line:

define(['jquery'], function($) {
   // in this callback $ can be used
});

The code above is very easy to understand:

every dependency in the array of the first argument
will be injected in the callback function at the same position

Let us combine jQuery with out own module from the Extension example

define(['jquery', 'TYPO3/CMS/FooBar/MyMagicModule'], function($, MyMagicModule) {
   // $ is our jQuery object
   // MyMagicModule is the object, which is returned from our own module
});