changes in js 2020

new.js

var regex = /t(e)(st(\d?))/g;
var string = 'test1test2';

string.match(regex); // gives ['test1', 'test2'] - how do i get the capturing groups?

var matches = [];
var lastIndexes = {};
var match;
lastIndexes[regex.lastIndex] = true;
while (match = regex.exec(string)) {
	lastIndexes[regex.lastIndex] = true;
	matches.push(match);
	// example: ['test1', 'e', 'st1', '1'] with properties `index` and `input`
}
matches;


matchAll(string, regex)

var s = "ECMAScript in 2020";

for (var w of s.matchAll(/\w+/g)) {
     print(w) // => "2020"
}

var r = /\w+/g;
var w;
while ((w = r.exec(s)) !==null) {
  print(w) // => "2020"
}

import defaultExport from "module-name";

  const main = document.querySelector("main");
  for (const link of document.querySelectorAll("nav > a")) {
    link.addEventListener("click", e => {
      // etc.
      import(`./${link}.js`)
        .then(module => {
          module.loadPageInto(main);
        })
        .catch(err => {
          // etc.
        });
    });
  }

function reflect(promise) {
  return promise.then(
    (v) => ({ status: 'fulfilled', value: v }),
    (error) => ({ status: 'rejected', reason: error })
  );
}

const promises = [ fetch('index.html'), fetch('https://does-not-exist/') ];
const results = await Promise.all(promises.map(reflect));
const successfulPromises = results.filter(p => p.status === 'fulfilled');


const promises = [ fetch('index.html'), fetch('https://does-not-exist/') ];
const results = await Promise.allSettled(promises);
const successfulPromises = results.filter(p => p.status === 'fulfilled');

2 ** 64
// => 18446744073709552000

2n ** 64n
// => 18446744073709551616n


const x = Number.MAX_SAFE_INTEGER;
// ↪ 9007199254740991, this is 1 less than 2^53

const y = x + 1;
// ↪ 9007199254740992, ok, checks out

const z = x + 2
// ↪ 9007199254740992, wait, that’s the same as above!




const theBiggestInt = 9007199254740991n;

const alsoHuge = BigInt(9007199254740991);
// ↪ 9007199254740991n

const biggerThanThat = theBiggestInt + 2n;
// ↪ 9007199254740993n

// optional chaining

var street = user.address ? user.address.street : undefined;
var result = user.method ? user.method() : undefined;
var dynamic = user.address ? user.address[field] : undefined;


var street = user.address?.street
var result = user.method?.();
var dynamic = user.address?.[field];


//nullish coalescing


const undefinedValue    =  undefined || 'default';   // 'default'
const nullValue         =  null || 'default';        // 'default'
const headerText        =  '' || 'Hello, world!';    // 'Hello, world!'
const animationDuration =  0 || 300;                 // 300
const showSplashScreen  =  false || true;            // true


const undefinedValue    =  undefined ?? 'default';   // 'default'
const nullValue         =  null ?? 'default';        // 'default'
const headerText        =  '' ?? 'Hello, world!';    // ''
const animationDuration =  0 ?? 300;                 // 0
const showSplashScreen  =  false ?? true;            // false


end