JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://code.angularjs.org/1.0.1/angular-1.0.1.js" ng:autobind></script>

<div ng:app="myApp">
<div ng:controller="Main">
    <p>Your lucky number: <input ng-model="luckynumber" ng-change="testNumber()"> (Your number is {{luckynumber}})</p>
</div>
</div>

JavaScript

angular.module('myApp', []);

function Main($scope) {
    $scope.luckynumber = null;

    $scope.testNumber = function() {
        if ($scope.luckynumber==7) {
            alert('The lucky number mustn\'t be equal 7.');
            $scope.luckynumber = null;
        }
    };
  
}