"Extension methods in JavaScript" via the prototype property.
Array.prototype.contains = function(value) {
for (var i = 0; i < this.length; i++) {
if (this[i] == value) return true;
}
return false;
}
This will add a contains method to all Array objects. You can call this method using this syntax stringArray.contains("foobar");
var stringArray = ["foo", "bar", "foobar"];
stringArray.contains("foobar");