use strict javascript

// Whole-Script Strict Mode Syntax
'use strict';
var v = "Hi! I'm a strict mode script!";// File: myscript.js

'use strict';
var a = 2;
....function doSomething() {
    'use strict';
    ...
}// Non-strict code...

(function(){
  "use strict";

  // Define your library strictly...
})();

// Non-strict code...