AngularJS: Using third party libraries without exposing a global variable

Question

What is the best way to use a third party library in Angular without exposing a global variable?

For instance, if I were using underscore.js, I want to inject _ into only the controllers that use it.

angular.module('module').controller(function(_) {
  // _ is injected only into this scope
};

To get this effect, I've seen some people load underscore globally with a script tag, then create a service like this:

myModule.factory('_', function ($window) {
    return $window._;
});

However, this still pollutes the global scope with _.

Is there an 'Angular way' of registering and injecting third party libraries without causing this problem?

Answer 1

You can't do anything about how the third party libraries are written, except by forking them and creating your own version.

Third party libraries will almost always create such variables on the global scope, and you mention the two most frequently used ways of using them in an Angular module: by injecting $window and using them directly, or by creating a thin service which provides the object.

I would favor the latter in most cases because it makes the code in other modules simpler. Also, in my mind, the service approach makes the code in your controllers seem less 'magic' and more debuggable, as it is clear where the library, e.g. _ comes from. Variables appearing "out of thin air" is some of the problem with global variables to begin with.

The library will still "pollute" the global scope, unless you explicitly deletes them from the global scope, perhaps after fetching a pointer to them in a service, which then can pass it on. However, I can't see any motivation for doing so. Any other attempts, such as using an Angular service to actually download the third party script and evaluating it, somehow preventing it from reaching the global scope, seems vastly inefficient, over-engineered and slow (both computationally and with regards to when HTTP requests are fired).

It's otherwise a good idea not to create any more global variables than strictly necessary.