javascript - Purpose to create anonymous function and call it immediately -

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i following angularjs tutorial, , encountered this:

(function(){     'use strict'     angular.module('users',['ngmaterial]); })();

i wondering difference between , this:

angular.module('users',['ngmaterial']);

as far understanding goes, both define new angularjs module, guessing there more it?

var module1=angular.module('users',['ngmaterial']);  console.log(window.module1);

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>

with above snippet. global variable , copied global object(window)

(function(){      'use strict'      var  module1=angular.module('users',['ngmaterial']);    console.log(module1);  })();

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>

with snippet, making not copy window(global) object , modularising code

hope helps

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