Add elements to the beginning of an array in JS

1. Use the Array.unshift() method

//向数组开头添加一个或多个元素，并返回新的长度，该方法改变原数组
let person= ['张三', '李四', '王五'];
console.log(person.unshift('小明')); // 4
console.log(person); // ["小明", "张三", "李四", "王五"]

2. Use the spread operator (…)

var arr1 = ['张三', '李四', '王五'];
var arr2 = ['小明', ...arr1];
console.log(arr2); // ["小明", "张三", "李四", "王五"]

3. Use the Aarry.concat() method

//用于连接两个或多个数组，并返回一个新数组，该方法不会改变原数组
var arr3 = ['aaa'];
console.log(arr3.concat(arr2)); // ["aaa", "小明", "张三", "李四", "王五"]
console.log(arr2); // ["小明", "张三", "李四", "王五"]