正则

命名捕获 ?

let str = '2019-03-21';
let reg = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/;
let {year, month, day} = str.match(reg).groups;  // match() 检索指定的值或找到一个或多个正则表达式的匹配
console.log(year, month, day);

反向引用 \k

let reg = /^(?<strive>welcome)-\k<strive>$/;
let str = 'welcome-welcome';
console.log(reg.test(str));  //--> true    test() 检测一个字符串是否匹配某个模式

let reg = /^(?<strive>welcome)-\k<strive>-\1$/;
let str = 'welcome-welcome-welcome';
console.log(reg.test(str));  //--> true

替换 $

let str = '2019-03-21';
let reg = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/;
str = str.replace(reg, '$<month>/$<day>/$<year>');  // replace() 用一些字符替换另一些字符
console.log(str);

dotAll模式 s

let reg = /^\w+.\w+$/s;  // 使 . 匹配之前匹配不了的
let str = 'abc\nbcd';
console.log(reg.test(str));  //--> true

按码点判断字符串长度 u

let str = 'abc奈斯';
let reg = /./u;
console.log(reg.test(str));  //--> true

具名引用

const RE_DATE = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/;

const matchObj = RE_DATE.exec("1999-12-31");
const year = matchObj.groups.year;
const month = matchObj.groups.month;
const day = matchObj.groups.day;

console.log(year, month, day);  //--> 1999 12 31

后行断言

/(?<=\$)\d+/.exec('Benjamin Franklin is on the $100 bill');  //--> ["100"]
/(?<!\$)\d+/.exec('it’s is worth about €90');  //--> ["90"]