// @target: es5
// @lib: es6,es2018

let re = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/u;
let result = re.exec("2015-01-02");

let date = result[0];

let year1 = result.groups.year;
let year2 = result[1];

let month1 = result.groups.month;
let month2 = result[2];

let day1 = result.groups.day;
let day2 = result[3];

let foo = "foo".match(/(?<bar>foo)/)!.groups.foo;