Javascript 数组合并

1.concat

let arr1=[1,2,3,4]
let arr2=[7,8,9,20]
let arr3=arr1.concat(arr2)
console.log(arr3)//[1, 2, 3, 4, 7, 8, 9, 20]

2. ...(es6展开符)

let arr4=[1,2,3,4]
let arr5=[7,8,9,20]
let arr6=[...arr4,...arr5]
console.log(arr6)

3.apply  Function.prototype.apply() - JavaScript | MDN

const array = ['a', 'b'];
const elements = [0, 1, 2];
array.push.apply(array, elements);
console.info(array); // ["a", "b", 0, 1, 2]