JavaScript判断数组是否包含指定元素的方法

/**
* Array.prototype.[method name] allows you to define/overwrite an objects method
* needle is the item you are searching for
* this is a special variable that refers to "this" instance of an Array.
* returns true if needle is in the array, and false otherwise
*/
Array.prototype.contains = function ( needle ) {
for (i in this) {
if (this[i] == needle) return true;
}
return false;
}

// Now you can do things like:
var x = Array();
if (x.contains('foo')) {
// do something special
}