Javascript Array find(element)

Array.prototype.find = function (element) {
 
 if (typeof element === 'function') {
  return element(this);
 }

 var len = this.length;
 
 for (var i = 0; i < len; i++) {
  if(this[i] === element) {
   return element;
  }/*from   w w w  . j a  va 2s .  c om*/
 }

 return -1;
}


// test function 
var doPow = function (array) {
 
 var len = array.length;
 
 for(var i = 0; i < len; i++) {
  array[i] *= array[i]; 
 }

 return array;
}


// test array
var b = [1, 2, 3, 4, 5, 6];

console.log(b.find(doPow));