ECMAScript 2020

JavaScript version number

Old JS versions are named by number: ES5 (2009) and ES6 (2015).

Starting from 2016, versions are named by year: ECMAScript 2016, 2017, 2018, 2019, ...

New features in ES2020:

Warning

These features are relatively new.

Older browsers may require alternative code (Polyfill).

JavaScript BigInt

JavaScript BigInt variables are used to store large integer values that cannot be represented by ordinary JavaScript numbers.

JavaScript integers can only be accurate to 15 digits.

Integer instance

let x = 999999999999999;
let y = 9999999999999999; // Too large

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BigInt instance

let x = 9999999999999999;
let y = 9999999999999999n;

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

Example

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

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The JavaScript type of BigInt is "bigint":

Example

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

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Since September 2020, all modern browsers have supported BigInt:

Chrome Edge Firefox Safari Opera
Chrome 67 Edge 79 Firefox 68 Safari 14 Opera 54
May 2018 January 2020 July 2019 September 2020 June 2018

JavaScript String Method matchAll()

Before ES2020, there was no string method available 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, you must set the global flag (g) or it will throw a TypeError.

Example

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

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If you want to perform a case-insensitive search, you must set the case-insensitive flag (i)

Example

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

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Hint:ES2021 The string method replaceAll() was introduced.

Nullish Coalescing Operator (Nullish Coalescing Operator) (?? Operator)

If the first parameter is not a nullish value (null or undefined），then ?? The operator returns the first parameter.

otherwise return the second.

Example

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

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Since March 2020, all modern browsers have supported nullish operators:

Chrome Edge Firefox Safari Opera
Chrome 80 Edge 80 Firefox 72 Safari 13.1 Opera 67
February 2020 February 2020 January 2020 March 2020 March 2020

Optional Chaining Operator (Optional Chaining Operator) (?. Operator)

If the object is undefined or nullthenOptional Chaining OperatorReturns undefined(instead of throwing an error).

Example

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

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Since March 2020, all modern browsers have supported ?.= Operator:

Chrome Edge Firefox Safari Opera
Chrome 80 Edge 80 Firefox 74 Safari 13.1 Opera 67
February 2020 February 2020 March 2020 March 2020 March 2020

Logical AND Assignment Operator (&&= Operator)

Logical AND Assignment Operatorused between two values.

If the first value is trueIf the first value is null or undefined, then assign the second value.

Logical AND Assignment Example

let x = 100;
x &&= 5;

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All modern browsers have supported since September 2020 &&= Operator:

Chrome Edge Firefox Safari Opera
Chrome 85 Edge 85 Firefox 79 Safari 14 Opera 71
August 2020 August 2020 March 2020 September 2020 September 2020

Logical OR Assignment Operator (||= Operator)

Logical OR Assignment Operatorused between two values.

If the first value is falseIf the first value is null or undefined, then assign the second value.

Logical OR Assignment Example

let x = 10;
x ||= 5;

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All modern browsers have supported since September 2020 ||= Operator:

Chrome Edge Firefox Safari Opera
Chrome 85 Edge 85 Firefox 79 Safari 14 Opera 71
August 2020 August 2020 March 2020 September 2020 September 2020

Nullish Coalescing Assignment Operator (??= Operator)

Nullish Coalescing Assignment Operator(Nullish Coalescing Assignment Operator) is used between two values.

If the first value undefined or undefined nullIf the first value is null or undefined, then assign the second value.

Nullish Coalescing Assignment Example

let x = 10;
x ??= 5;

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All modern browsers have supported since September 2020 ??= Operator:

Chrome Edge Firefox Safari Opera
Chrome 85 Edge 85 Firefox 79 Safari 14 Opera 71
August 2020 August 2020 March 2020 September 2020 September 2020