ECMAScript 2020

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JavaScript Version Numbers

Old ECMAScript versions was named by numbers: ES5 and ES6.

From 2016, versions are named by year: ES2016, 2018, 2020 ...

New Features in ES2020

BigInt
String matchAll()
The Nullish Coalescing Operator (??)
The Optional Chaining Operator (?.)
Logical AND Assignment Operator (&&=)
Logical OR Assignment (||=)
Nullish Coalescing Assignment (??=)
Promise.allSettled()
Dynamic Import

Warning

These features are relatively new.

Older browsers may need an alternative code (Polyfill)

JavaScript BigInt

JavaScript BigInt variables are used to store big integer values that are too big to be represented by a a normal JavaScript Number.

JavaScript integers are only accurate up to about 15 digits.

Integer Example

let x = 999999999999999;
let y = 9999999999999999; // too big

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BigInt Example

let x = 9999999999999999;
let y = 9999999999999999n;

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To create a BigInt, append n to the end of an integer or call BigInt():

Example

let x = 1234567890123456789012345n;
let y = BigInt(1234567890123456789012345)

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The JavaScript typeof a BigInt is "bigint":

Example

let x = BigInt(999999999999999);
let type = typeof x;

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BigInt is supported in all modern browsers since September 2020:


Chrome 67	Edge 79	Firefox 68	Safari 14	Opera 54
May 2018	Jan 2020	Jul 2019	Sep 2020	Jun 2018

JavaScript String matchAll()

Before ES2020 there was no string method that could be used to search for all occurrences of a string in a string.

Example

const iterator = text.matchAll("Cats");

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If the parameter is a regular expression, the global flag (g) must be set set, otherwise a TypeError is thrown.

Example

const iterator = text.matchAll(/Cats/g);

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If you want to search case insensitive, the insensitive flag (i) must be set:

Example

const iterator = text.matchAll(/Cats/gi);

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Note

ES2021 introduced the string method replaceAll().

The Nullish Coalescing Operator (??)

The ?? operator returns the first argument if it is not nullish (null or undefined).

Otherwise it returns the second.

Example

let name = null;
let text = "missing";
let result = name ?? text;

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The nullish operator is supported in all modern browsers since March 2020:


Chrome 80	Edge 80	Firefox 72	Safari 13.1	Opera 67
Feb 2020	Feb 2020	Jan 2020	Mar 2020	Mar 2020

The Optional Chaining Operator (?.)

The Optional Chaining Operator returns undefined if an object is undefined or null (instead of throwing an error).

Example

const car = {type:"Fiat", model:"500", color:"white"};
let name = car?.name;

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The ?.= operator is supported in all modern browsers since March 2020:


Chrome 80	Edge 80	Firefox 74	Safari 13.1	Opera 67
Feb 2020	Feb 2020	Mar 2020	Mar 2020	Mar 2020

The &&= Operator

The Logical AND Assignment Operator is used between two values.

If the first value is true, the second value is assigned.

Logical AND Assignment Example

let x = 10;
x &&= 5;

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The &&= operator is supported in all modern browsers since September 2020:


Chrome 85	Edge 85	Firefox 79	Safari 14	Opera 71
Aug 2020	Aug 2020	Mar 2020	Sep 2020	Sep 2020

The ||= Operator

The Logical OR Assignment Operator is used between two values.

If the first value is false, the second value is assigned.

Logical OR Assignment Example

let x = 10;
x ||= 5;

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The ||= operator is supported in all modern browsers since September 2020:


Chrome 85	Edge 85	Firefox 79	Safari 14	Opera 71
Aug 2020	Aug 2020	Mar 2020	Sep 2020	Sep 2020

The ??= Operator

The Nullish Coalescing Assignment Operator is used between two values.

If the first value is undefined or null, the second value is assigned.

Nullish Coalescing Assignment Example

let x;
x ??= 5;

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The ??= operator is supported in all modern browsers since September 2020:


Chrome 85	Edge 85	Firefox 79	Safari 14	Opera 71
Aug 2020	Aug 2020	Mar 2020	Sep 2020	Sep 2020

JavaScript Promise.allSettled()

The Promise.allSettled() method returns a single Promise from a list of promises.

Example

// Create a Promise
const myPromise1 = new Promise((resolve, reject) => {
  setTimeout(resolve, 200, "King");
});

// Create another Promise
const myPromise2 = new Promise((resolve, reject) => {
  setTimeout(resolve, 100, "Queen");
});

// Settle All
Promise.allSettled([myPromise1, myPromise2]).then((results) =>
  results.forEach((x) => myDisplay(x.status)),
);

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Promise.allSettled() is supported in all modern browsers since March 2020:


Chrome 76	Edge 79	Firefox 71	Safari 13	Opera 63
May 2019	Nov 2019	Mar 2020	Sep 2019	Aug 2019

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