在javascript中使用数组更新存储的数组

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

let arr = [1, 2, 3];
arr.pop();
console.log(arr); // [1, 2]

let arr = [1, 2, 3];
arr.splice(1, 0, 4); // 在索引为1的位置添加元素4
console.log(arr); // [1, 4, 2, 3]

arr.splice(2, 1); // 删除索引为2的元素
console.log(arr); // [1, 4, 3]

let arr1 = [1, 2];
let arr2 = [3, 4];
let newArr = arr1.concat(arr2);
console.log(newArr); // [1, 2, 3, 4]

let arr = [1, 2, 3];
let newArr = arr.map((item) => item * 2);
console.log(newArr); // [2, 4, 6]

let arr = [1, 2, 3, 4, 5];
let newArr = arr.filter((item) => item % 2 === 0);
console.log(newArr); // [2, 4]