ES2018：RegExp 新功能介紹

const input = `
Lorem ipsum dolor sit amet, consectetur adipiscing hello
world elit. Nam sit amet elit id risus aliquam porta.
`;

/hello.world/u.test(input);
// false

/hello[\s\S]world/u.test(input);
// true

/hello[^]world/u.test(input)
// true

/hello.world/su.test(input);
// true

const pattern = /(\d{4})-(\d{2})-(\d{2})/u;
const result = pattern.exec('2018-05-09');
// result[0] === '2018-05-09'
// result[1] === '2018'
// result[2] === '05'
// result[3] === '09'

const pattern = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/u;
const result = pattern.exec('2018-05-09');
// result.groups.year === '2018'
// result.groups.month === '05'
// result.groups.day === '09'

const regexGreek = /\p{Script_Extensions=Greek}/u;
regexGreek.test('π');
// true

const regexAscii = /\p{ASCII}/u;
regexAscii.test('_');
// true

const regexMath = /\p{Math}/u;
regexMath.test('≠');
// true

const pattern = /[\p{Letter}\p{White_Space}]+/u;
pattern.test('πüé μετά Grüß');
// true

<style>
  :valid { background: lightgreen; }
  :invalid { background: pink; }
</style>
<input pattern="[\p{Letter}\p{White_Space}]+" value="your input string">

// Positive lookahead:
const pattern = /\d+(?= dollars)/u;
const result = pattern.exec('42 dollars');
// result[0] === '42'

// Negative lookahead:
const pattern = /\d+(?! dollars)/u;
const result = pattern.exec('42 rupees');
// result[0] === '42'

// Positive lookbehind:
const pattern = /(?<=\$)\d+/u;
const result = pattern.exec('$42');
// result[0] === '42'

// Negative lookbehind:
const pattern = /(?<!\$)\d+/u;
const result = pattern.exec('#42');
// result[0] === '42';

const string = 'Magic hex numbers: DEADBEEF CAFE 8BADF00D';
const regex = /\b\p{ASCII_Hex_Digit}+\b/gu;
let match;

// 以前要這樣寫
while (match = regex.exec(string)) {
  console.log(match);
}

// matchAll:
for (const match of string.matchAll(regex)) {
  console.log(match);
}