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JS Tutorial

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JS Objects

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JS Functions

Function Definitions Function Parameters Function Invocation Function Call Function Apply Function Bind Function Closures

JS Classes

Class Intro Class Inheritance Class Static

JS Async

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JS HTML DOM

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JS Browser BOM

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JS Web APIs

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JS AJAX

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JS JSON

JSON Intro JSON Syntax JSON vs XML JSON Data Types JSON Parse JSON Stringify JSON Objects JSON Arrays JSON Server JSON PHP JSON HTML JSON JSONP

JS vs jQuery

jQuery Selectors jQuery HTML jQuery CSS jQuery DOM

JS Graphics

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JS Examples

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JS References

JavaScript Objects HTML DOM Objects


ECMAScript 2021

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 ES2021

Warning

These features are relatively new.

Older browsers may need an alternative code (Polyfill)

JavaScript Promise.any()

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");
});

// Run when any promise fulfill
Promise.any([myPromise1, myPromise2]).then((x) => {
  myDisplay(x);
});
Try it Yourself »

Promise.any() is supported in all modern browsers since September 2020:

Chrome 85 Edge 85 Firefox 79 Safari 14 Opera 71
Aug 2019 Aug 2020 Jul 2020 Sep 2020 Sep 2020

JavaScript String ReplaceAll()

ES2021 introduced the string method replaceAll():

Example

text = text.replaceAll("Cats","Dogs");
text = text.replaceAll("cats","dogs");
Try it Yourself »

The replaceAll() method allows you to specify a regular expression instead of a string to be replaced.

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

Example

text = text.replaceAll(/Cats/g,"Dogs");
text = text.replaceAll(/cats/g,"dogs");
Try it Yourself »

Note

ES2020 introduced the string method matchAll().



JavaScript Numeric Separator (_)

ES2021 intoduced the numeric separator (_) to make numbers more readable:

Example

const num = 1_000_000_000;
Try it Yourself »

The numeric separator is only for visual use.

Example

const num1 = 1_000_000_000;
const num2 = 1000000000;
(num1 === num2);
Try it Yourself »

The numeric separator can be placed anywhere in a number:

Example

const num1 = 1_2_3_4_5;
Try it Yourself »

Note

The numeric separator is not allowed at the beginning or at the end of a number.

In JavaScript only variables can start with _.

The numeric separator is supported in all modern browsers since January 2020:

Chrome 75 Edge 79 Firefox 74 Safari 13.1 Opera 67
Jun 2019 Jan 2020 Oct 2019 Sep 2019 Jun 2019


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