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JS Objects

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JS Functions

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JS Classes

Class Intro Class Inheritance Class Static

JS Async

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JS HTML DOM

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JS JSON

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ECMAScript 2022

JavaScript Version Numbers

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

From 2016, versions are named by year: ES2016, 2018, 2020, 2022.

New Features in ES2022


Warning

These features are relatively new.

Older browsers may need an alternative code (Polyfill)


JavaScript Array at()

ES2022 intoduced the array method at():

Examples

Get the third element of fruits:

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let fruit = fruits.at(2);
Try it Yourself »

Get the third element of fruits:

const fruits = ["Banana", "Orange", "Apple", "Mango"];
let fruit = fruits[2];
Try it Yourself »

The at() method returns an indexed element from an array.

The at() method returns the same as [].

The at() method is supported in all modern browsers since March 2022:

Chrome 92 Edge 92 Firefox 90 Safari 15.4 Opera 78
Apr 2021 Jul 2021 Jul 2021 Mar 2022 Aug 2021

Note

Many languages allows negative bracket indexing like [-1] to access elements from the end of an object / array / string.

This is not possible in JavaScript, because [] is used for accessing both arrays and objects. obj[-1] refers to the value of key -1, not to the last property of the object.

The at() method was introduced in ES2022 to solve this problem.


JavaScript String at()

ES2022 intoduced the string method at():

Examples

Get the third letter of name:

const name = "W3Schools";
let letter = name.at(2);
Try it Yourself »

Get the third letter of name:

const name = "W3Schools";
let letter = name[2];
Try it Yourself »

The at() method returns an indexed element from an string.

The at() method returns the same as [].

The at() method is supported in all modern browsers since March 2022:

Chrome 92 Edge 92 Firefox 90 Safari 15.4 Opera 78
Apr 2021 Jul 2021 Jul 2021 Mar 2022 Aug 2021

RegExp d Modifier

ES2022 added the /d modifier to express the start and end of the match.

Example

let text = "aaaabb";
let result = text.match(/(aa)(bb)/d);
Try it Yourself »

RegExp Modifiers are used to spescfy case-insensitive, and other global searches:

Modifier Description Try it
i Perform case-insensitive matching Try it »
g Perform a global match (find all) Try it »
m Perform multiline matching Try it »
d Perform substring matches (New in ES2022) Try it »

Object hasOwn

ES2022 provides a safe way to check if a property is the own property of an object.

Object.hasOwn() is similar to Object.prototype.hasOwnProperty but supports all object types.

Example

Object.hasOwn("initProp")
Try it Yourself »

Error Cause

ES2022 let you specify the reason behind an error with error.cause.

Example

try { connectData(); } catch (err) { throw new Error("Connecting failed.", { cause: err }); }
Try it Yourself »


JavaScript await import

JavasSript modules can now wait for resources that require import before running:

import {myData} from './myData.js';

const data = await myData();

JavaScript Class Field Declarations

class Hello {
  counter = 0; // Class field
}
const myClass = new Hello();

let x = myClass.counter;

Class Field Declarations is supported in all modern browsers since April 2021:

Chrome 72 Edge 79 Firefox 69 Safari 14.1 Opera 60
Jan 2019 Jan 2020 Sep 2019 Apr 2021 Jan 2020

JavaScript Private Methods and Fields

class Hello {
  #counter = 0;  // Private field
  #myMethod() {} // Private method
}
const myClass = new Hello();

let x = myClass.#counter; // Error
myClass.#myMethod();      // Error

Private Methods and Fields is supported in all modern browsers since June 2021:

Chrome 74 Edge 79 Firefox 90 Safari 14.1 Opera 62
Apr 2019 Jan 2020 Jun 2021 Apr 2021 Jun 2019


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