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splice(下标，个数)是操作数组的方法，返回被删除的元素，操作后原数组会被改变

splice()只有1个参数时：

let arr = [1,2,3,4,5,6,7,8,9]let arr1 = arr.splice(3)//包含该下标元素，删除后面所有的console.log(arr)  //[1, 2, 3]console.log(arr1)  //[4, 5, 6, 7, 8, 9]

splice()有2个参数时：

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.splice(1,3) //(起始下标1，删除3个) console.log(arr)  //[1, 5, 6, 7, 8, 9] console.log(arr1)  //[2, 3, 4]

splice()有3个参数或多个时：

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.splice(1,5,20)  //(起始下标1，删除5个，20插入到起始下标的位置) console.log(arr)  //[1, 20, 7, 8, 9] console.log(arr1)  //[2, 3, 4, 5, 6]

参数为负数：

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.splice(-2) console.log(arr)  //[1, 2, 3, 4, 5, 6, 7] console.log(arr1)  //[8, 9]

如果第2个参数为负数，视为0：

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.splice(-2,-4) console.log(arr)  //[1, 2, 3, 4, 5, 6, 7] console.log(arr1)  //[]

slice(起始下标，结束下标)可以操作数组和字符串，不改变原数组或字符串，返回被截取的元素

slice()操作数组时：

let arr = [1,2,3,4,5,6,7,8,9]let arr1 = arr.slice(3)//包含该下标元素，删除后面所有的console.log(arr)  // [1, 2, 3, 4, 5, 6, 7, 8, 9]console.log(arr1)  // [4, 5, 6, 7, 8, 9]

slice()有2个参数时：

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.slice(3,6) //（包含的起始下标，不包含的结束下标） console.log(arr)  // [1, 2, 3, 4, 5, 6, 7, 8, 9] console.log(arr1)  // [4, 5, 6]

第3个或多个参数无效

参数为负数：

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.slice(3,-2) //(从左开始截取下标，负数从右开始截取下标) console.log(arr)  // [1, 2, 3, 4, 5, 6, 7, 8, 9] console.log(arr1)  // [4, 5, 6, 7]

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.slice(-4,-2) //(负数从右开始截取下标，负数从右开始截取下标) console.log(arr)  // [1, 2, 3, 4, 5, 6, 7, 8, 9] console.log(arr1)  // [6, 7]

如果第二个负数参数的位置超过第一个参数的位置，则返回 [ ]

let arr = [1,2,3,4,5,6,7,8,9] let arr1 = arr.slice(3,-6) console.log(arr)  // [1, 2, 3, 4, 5, 6, 7, 8, 9] console.log(arr1)  // []

slice()操作字符串时，参数情况和返回结果跟数组是一样的

let arr = 'abcdefghijklmn' let arr1 = arr.slice(2,4) console.log(arr)  // abcdefghijklmn console.log(arr1)  // cd

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