var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope) {
  $scope.myForm = {};
  $scope.formData = {
    lovingAngular: 'YES'
  };
});
<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.5.x" src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.5.11/angular.min.js" data-semver="1.5.11"></script>
    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <form name="myForm">
      <label>
        <input type="checkbox" name="lovingAngular" ng-model="formData.lovingAngular"
               ng-true-value="'YES'" ng-false-value="'NO'">
        Loving Angular?
       </label>
    </form>
    
    <tt>{{ formData | json }}</tt><br/>
  
  </body>

</html>
/* Put your css in here */