删除指定下标数组元素  
Array.prototype.del=function(index){  
        if(isNaN(index)||index>=this.length){  
            return false;  
        }  
        for(var i=0,n=0;i<this.length;i++){  
            if(this[i]!=this[index]){  
                this[n++]=this[i];  
            }  
        }  
        this.length-=1;  
    };  
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());  
        }