实例如下：
=this.length){
return false;
}
for(var i=0,n=0;i删除指定元素
Array.prototype.indexOf = function(val) {
for (var i = 0; i < this.length; i++) {
if (this[i] == val) return i;
}
return -1;
};
Array.prototype.remove = function(val) {
var index = this.indexOf(val);
if (index > -1) {
this.splice(index,1);
}
};
function a(){
var arr = [1,2,3,4,5];
alert(arr.toString());
arr.remove(3);
alert(arr.toString());
} </pre>