Count the frequency of an element within an array, returns length if the argument is undefined

array.count.js

if(!Array.prototype.count){
	Array.prototype.count = function(el){
		if(typeof(el) === "undefined"){
			return this.length;
		}else{
			var count = 0;
			for(i = 0; i < this.length; i++){
				if(this[i] === el){
					count++;
				}
			}
			return count;
		}
	}
}