splice，非源码

初步简单模拟splice方法，有助于深刻理解和记忆

Array.prototype.savaSplice = function (m, n) {
//创建数组副本
let clone = []
clone.push(…this)

//创建数据，用于保存被裁剪的数据
let afterSplice = []

let len = this.length

for (let i = 0; i < len; i++) {
    if (i === m) {
        for (let j = i; j < len; j++) {
            clone.pop()
        }
        for (let k = i + n; k < len; k++) {
            clone.push(this[k])
        }
        for (let l = 0; l < n; l++) {
            afterSplice.push(this[i + l])
        }
    }
}

for (let s = 0; s < len; s++) {
    this.pop()
}
this.push(...clone)

return afterSplice

}

let arr1 = [1, 3, 6, 2, 6, 9, 6, 3]

let arr2 = arr1.savaSplice(4, 2)
console.log(arr1, arr2) //[ 1, 3, 6, 2, 6, 3 ] [ 6, 9 ]