Javascript의 최신 기능

Modern JavaScript features you may have missed

http://www.breck-mckye.com/blog/2019/10/modern-javascript-features-you-may-have-missed/

개발에만 집중하게 되면 놓칠 수 있는 자바스크립트 최신 기능

ES2015

Binary and octal literals

2진수 변경 0b

const binaryZero = 0b0;
const binaryOne  = 0b1;
const binary255  = 0b11111111;
const binaryLong = 0b111101011101101;

8진수 변경 0o

// Pizza toppings
const olives    = 0b0001;
const ham       = 0b0010;
const pineapple = 0b0100;
const artechoke = 0b1000;

const pizza_ham_pineapple = pineapple | ham;
const pizza_four_seasons  = olives | ham | artechoke;

Number.isNaN()

isNaN()

isNaN(NaN)              === true
isNaN(null)             === false
isNaN(undefined)        === true
isNaN({})               === true
isNaN('0/0')            === true
isNaN('hello')          === true

Number.isNaN()

Number.isNaN(NaN)       === true
Number.isNaN(null)      === false
Number.isNaN(undefined) === false
Number.isNaN({})        === false
Number.isNaN('0/0')     === false
Number.isNaN('hello')   === false

ES2016

Exponent (power) operator

Transpilers : @babel/plugin-transform-exponentiation-operator

2**2 === 4
3**2 === 9
3**3 === 27

Array.prototype.includes()

Transpilers : babel-plugin-array-includes

[1, 2, 3].includes(2)    === true
[1, 2, 3].includes(true) === false

const object1 = {};
const object2 = {};

const array = [object1, 78, NaN];

array.includes(object1) === true
array.includes(object2) === false
array.includes(NaN)     === true

// positions   0  1  2  3  4
const array = [1, 1, 1, 2, 2];

array.includes(1, 2) === true
array.includes(1, 3) === false

ES2017

Shared Array Buffers & Atomics

브라우저 프로세스간에 메모리를 직접적으로 공유하고, 경쟁 조건을 피하도록 할수 있는 기능 이것의 기능은 아래의 URL에서 참고 하도록 하자

https://www.sitepen.com/blog/the-return-of-sharedarraybuffers-and-atomics/

ES2018

Regex bonanza

ES2018의 새로운 정규 표현식의 기능

Lookbehind matches (match on previous chars)

const regex = /(?<=\$)\d+/;
const text  = 'This cost $400';
text.match(regex) === ['400']

Look ahead:  (?=abc)
Look behind: (?<=abc)

Look ahead negative:  (?!abc)
Look behind negative: (?<!abc)

You can name capture groups

const getNameParts  = /(\w+)\s+(\w+)/g;
const name          = "Weyland Smithers";
const subMatches    = getNameParts.exec(name);

subMatches[1]     === 'Weyland'
subMatches[2]     === 'Smithers'

const getNameParts  = /(?<first>\w+)\s(?<last>\w+)/g;
const name          = "Weyland Smithers";
const subMatches    = getNameParts.exec(name);

const {first, last} = subMatches.groups
first             === 'Weyland'
last              === 'Smithers'

ES2019

Array.prototype.flat() & flatMap()

const multiDimensional = [
	[1, 2, 3],
    [4, 5, 6],
    [7,[8,9]]
];

multiDimensional.flat(2) === [1, 2, 3, 4, 5, 6, 7, 8, 9]

const texts = ["Hello,", "today I", "will", "use FlatMap"];

// with a plain map
const mapped = texts.map(text => text.split(' '));
mapped === ['Hello', ['today', 'I'], 'will', ['use', 'FlatMap']];

// with flatmap
const flatMapped = texts.flatMap(text => text.split(' '));
flatMapped === ['Hello', 'today', 'I', 'will', 'use', 'FlatMap'];

Unbound catches

try {
  // something throws
} catch {
  // don't have to do catch(e)
}

String trim methods

const padded         = '          Hello world   ';
padded.trimStart() === 'Hello world   ';
padded.trimEnd()   === '          Hello world';