（func）（）和（func）.call（window）之间的区别

Question

I am studying how to create some plugins using angularjs and in some of them I have faced this:

(function() {
    'use strict'
    //code...
}).call(window);

what is the difference from just using a self-invoking function like that below?

(function() {
    'use strict'
    //code...
})();

Answer 1

The two invocations will have different this values.

This code

(function() {
    'use strict'
    console.log(this)
})();

will log undefined because direct non-method invocations of strict-mode functions use a this value of undefined .

This code

(function() {
    'use strict'
    console.log(this)
}).call(window);

will log window since the first argument to call is used to supply this to the function being invoked.

If I had to guess, I'd say this is being done to mimic the non-strict behavior of using window (instead of undefined ) for this of a bare non-method invocation. Simply use window if you mean window .