title: angular.isUndefined & angular.equals in angular 2
body: <p>I just began to try to migrate from angular 1 to 2, actually from ionic 1 to 2, and one of my first compilation error is that angular.isUndefined and angular.equals aren't resolved.</p>
  
  <p>How should I fix that, any tips?</p>
  
  <pre><code>namespace Utils {
  
  export class Comparator {
  
      static isEmpty(obj:any):boolean {
          return obj == null || Object.keys(obj).length === 0;
      }
  
      static isNumberNullOrZero(obj:number):boolean {
          return obj == null || obj === 0;
      }
  
      static equals(obj1:any, obj2:any):boolean {
          return angular.equals(obj1, obj2); // &lt;== here angular unresolved
      }
  
      static isStringEmpty(str:string):boolean {
          return !str || 0 === str.length;
      }
  
      static isStringBlank(str:string):boolean {
          return !str || /^\s*$/.test(str);
      }
  
      static isBiggerThanZero(num:number):boolean {
          return num != null &amp;&amp; !angular.isUndefined(num) &amp;&amp; num &gt; 0; // &lt;== here angular unresolved
      }
  
    }
  }
  </code></pre>