ES2018(ES9)新增

1、命名捕获

 let str = '2018-03-20';
 let reg = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/;
 let {year, month ,day} = str.match(reg).groups;
 console.log(year, month, day); // 2018,03,20

2、反向引用命名捕获
语法：\k<名字>

let reg = /^(?<Strive>welcome)-\k<Strive>$/; // 匹配: 'welcome-welcome-welcome'
let reg = /^(?<Strive>welcome)-\k<Strive>-\1$/;   // 匹配: 'welcome-welcome-welcome'   

3、替换

let str = '2018-03-20';
let reg = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/;
str = str.replace(reg,'$<day>/$<month>/$<year>');
console.log(str);  //  20/03/2018

replace接收一个函数

let str = '2018-03-20';
let reg = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/;
str = str.replace(reg, (...args)=>{
    //console.log(args)
    let {year, month, day} = args[args.length-1];
    return `${day}/${month}/${year}`;
});
console.log(str);   // 20/03/2018