AngularJS Example:

HTML

<div ng-app="app">
    <div ng-controller="Controller">
        <input type="text" ng-model="num" ng-change="formatNumber()" />
{{num}}
    </div>
</div>

JavaScript

angular.module('app', [])
	.controller('Controller', function ($scope,$filter) {
        $scope.formatNumber = function() {
          $scope.num = $filter('number')($scope.num);
        }
	});