Searching a Javascript Array

gistfile1.js

// Index of
var arr=["one","two","three"];
arr.indexOf('two'); // 1
arr.indexOf('four'); // -1

// Prototyping
Array.prototype.exists = function(o) {
for(var i = 0; i < this.length; i++)
   if(this[i] === o)
     return true;
return false;
}