数组中的参数调换位置

调换数组中3和4的位置，也就是下标为2，3的位置

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

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

var t = arr[2];
arr[2] =arr[3];
arr[3] = t
console.log(arr)  //[1, 2, 4, 3, 5, 6]

arr[3] = [arr[2],arr[2]=arr[3]][0]
console.log(arr)  //[1, 2, 4, 3, 5, 6]

arr.splice(2, 1, ...arr.splice(3, 1, arr[2]))
//[...iterator]得到原数组的索引,比如[...[6,6,6]]会输出[6,6,6]
console.log(arr);//[1, 2, 4, 3, 5, 6]