AngularJS Example:

HTML

<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css">
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>

<div ng-app='myModule' ng-controller='myController'>
  {{ someNumber }}
</div>

JavaScript

angular.module('myModule', [])

.factory('utilsFactory', function() {

var fun1 = function(a, b, c, d) {
    var x = a + b + c + d;
    return x;
};

var fun2 = function() {
    var x = fun1(1, 1, 1, 1);
    return x;
};

return {
    fun1: fun1,
    fun2: fun2
};
})

.controller('myController', ['$scope', 'utilsFactory', function($scope, utilsFactory) {
  $scope.someNumber = utilsFactory.fun2();
}]);