I'm importing Angular 1.4 in my entry point module of Webpack build as a CommonJS module (i.e. with var angular = require("angular");), but somehow it becomes available in global namespace of the browser (i.e. as window.angular, if I'm not mistaken).

In the source code of Angular 1.4 I found the following lines:

(function(window, document, undefined) {'use strict';

...

var
    msie,             // holds major version number for IE, or NaN if UA is not IE.
    jqLite,           // delay binding since jQuery could be loaded after us.
    jQuery,           // delay binding
    slice             = [].slice,
    splice            = [].splice,
    push              = [].push,
    toString          = Object.prototype.toString,
    getPrototypeOf    = Object.getPrototypeOf,
    ngMinErr          = minErr('ng'),

    /** @name angular */
    angular           = window.angular || (window.angular = {}),
    angularModule,
    uid               = 0;

So, do I get it right, that upon require, this line:

angular           = window.angular || (window.angular = {})

checks, if global angular object is available and if it is not, creates it. So, angular silently introduces side-effect? What's the purpose of () around window.angular = {}?

I'm importing Angular 1.4 in my entry point module of Webpack build as a CommonJS module (i.e. with var angular = require("angular");), but somehow it becomes available in global namespace of the browser (i.e. as window.angular).

In the source code of Angular 1.4 I found the following lines:

(function(window, document, undefined) {'use strict';

...

var
    msie,             // holds major version number for IE, or NaN if UA is not IE.
    jqLite,           // delay binding since jQuery could be loaded after us.
    jQuery,           // delay binding
    slice             = [].slice,
    splice            = [].splice,
    push              = [].push,
    toString          = Object.prototype.toString,
    getPrototypeOf    = Object.getPrototypeOf,
    ngMinErr          = minErr('ng'),

    /** @name angular */
    angular           = window.angular || (window.angular = {}),
    angularModule,
    uid               = 0;

So, do I get it right, that upon require, this line:

angular           = window.angular || (window.angular = {})

checks, if global angular object is available and if it is not, creates it. So, angular silently introduces side-effect?