JavaScript原型

var arr1=new Array(12,5,6,7);
var arr2=new Array(13,2,4,3);
//原型, arr1 arr2都属于array方法
Array.prototype.sum=function(){
	var result=0;
	var i=0;
	for(var i=0;i<this.length;i++){
		result+=this[i];
	}
	return result;
};

alert(arr1.sum());
alert(arr2.sum());