javascript 判断数组是否已包含了某个元素的函数

Array.prototype.contains = function(obj) { 
var i = this.length; 
while (i–) { 
if (this[i] === obj) { 
return true; 
} 
} 
return false; 
}

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