1.
<script>
/*splice(start,len)从那个位置开始删除几项*/
var arr = [1,2,3,4,5,6];
var removed = arr.splice(2,3);
alert(arr);//[1,2,6] // 从下标为2的位置往后删除3个
alert(removed)//[3,4,5]
/*splice(start,len,...) 当len 为 0 的时候为插入*/
var arr2 = [1,2,3,4,5];
var removed = arr2.splice(2,0,"a","b","c"); //从下标为2的位置删除0个，然后插入"a","b","c"
var removed = arr2.splice(2,0,["a","b","c"]); //从下标为2的位置删除0个，然后插入["a","b","c"]
alert(arr2); // [1,2,"a","b","c",3,4,5]
alert(removed == undefined);//空
/*splice(start,len,...) ，当len不为0的时候*/
var arr3 = ["hello","world","js","java"];
var removed = arr3.splice(1,2,[1,2,3,4,5,6]);//先从下标为1的位置往后删除2个元素，然后添加数组进来
alert(arr3);//["hello","java",1,2,3,4,5,6]
alert(removed );//["world","js"]
</script>