Question

I started to read several tutorials about RequireJS. In none of them was the “define” keyword explained satisfactorily for me. Could someone help me with the following :

define(
  ["Models/Person", "Utils/random", "jquery"], 
  function (Person, randomUtility, $) {..}
)  

What is “define”? Is define a function with an array and an anonymous function inside of it? Or is it something else? Can someone give me more information about this kind of definitions?

Addition: Thank you nnnnnn and pradeek for your answers. Here in Europe it was 2:30 in the night when I was posting the question. Maybe therefore I didn’t recognize it was a simple function call.

Answer 1

define is not specific to RequireJS, it is part of the AMD specification. Burke will note that RequireJS doesn’t implement exactly how AMD specifies it, since AMD didn’t really keep browsers in mind.

define doesn’t have an anonymous function in it. define is a method made available to AMD based JavaScript files for loading their data. Libraries like RequireJS make this available to you. The specific implementation probably isn’t valuable to you. So I’ll go over the one you provided as it’s the most common way to declare a module.

define( [array], object );

Array is a list of modules that this module depends on. There is a 1 to 1 relationship between modules and files. You can not have multiple modules in a file nor multiple files for one module.

Object is the module you are defining. This can be anything, a struct, or a function that returns a struct. Read the docs on RequireJS for more details.

If object is a function, the arguments passed to the function are the modules listed as dependencies in the first define argument. It is also important to note than when you pass a function as object, it will only run one time. The methods or properties created on this one instantiation can be accessed at any time though, can then be accessed by other modules that list this module as a dependency.

Good luck, I recommend playing around with this and reading the docs when things don’t make sense. RequireJS docs are great as a quick start on how AMD modules work.