数组 slice 和 splice

// 返回数组片段

var arr = [1,2,3,4,5,6];

console.log(arr.slice(1,3)); // [2, 3]
console.log(arr.slice(1)); // [2, 3, 4, 5, 6]
console.log(arr.slice(1,-1)); // [2, 3, 4, 5]
console.log(arr.slice(-4, -3)); // [3]

 * 原数组不会被修改

var arr = [1,2,3,4,5,6];

// console.log(arr.splice(2,2)); // 从索引2开始删除两个
// console.log(arr);
console.log(arr.splice(1,4,7,8,9,0,'a','b')); // 从索引1开始删除4个
console.log(arr); // [1, 7, 8, 9, 0, "a", "b", 6]

* 原数组会被修改