ECMAScript 2022

JavaScript versionsnummer

Gamle ECMAScript-versioner er navngivet efter tal: ES5 og ES6.

Fra 2016 har versionerne været navngivet efter år: ES2016, 2018, 2020, 2022.

Nye funktioner i ES2022

• Array at()
• String at()
• RegExp /d
• Object.hasOwn()
• error.cause
• await import
• Klassefeltdeklaration
• Privatmetoder og felter

JavaScript Array at()

ES2022 har introduceret arraymetoder at():

Eksempel 1

Få tredje element i arrayet 'fruits':

const fruits = ['Banana', 'Orange', 'Apple', 'Mango'];
let fruit = fruits.at(2);

Try it yourself

Eksempel 2

Få tredje element i arrayet 'fruits':

const fruits = ['Banana', 'Orange', 'Apple', 'Mango'];
let fruit = fruits[2];

Try it yourself

at() Metoden returnerer elementet på den angivne indeks fra arrayet.

at() Method is equivalent to [] The results returned are the same.

From March 2022, all modern browsers support at() Method:

JavaScript String at()

ES2022 har introduceret strengmetoder at():

Eksempel 1

Få tredje bogstavet i strengen 'name':

const name = "W3Schools";
let letter = name.at(2);

Try it yourself

Eksempel 2

Få tredje bogstavet i strengen 'name':

const name = "W3Schools";
let letter = name[2];

Try it yourself

at() Method returns the character at the specified index from the string.

at() Method is equivalent to [] The results returned are the same.

From March 2022, all modern browsers support at() Method:

RegExp d modifier

ES2022 added /d Modifiers, used to indicate the start and end of the match.

Instance

let text = "aaaabb";
let result = text.match(/(aa)(bb)/d);

Try it yourself

RegExp modifiers are used to specify case-insensitive matching and other global searches:

Object.hasOwn()

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

Object.hasOwn() Similar to Object.prototype.hasOwnPropertybut supports all object types.

Instance

Object.hasOwn(myObject, age)

Try it yourself

Error Cause

ES2022 allows you to specify the root cause of an error through error.cause.

Instance

connectData(); 
  catch (err) { 
} 
  throw new Error("Connecting failed.", { cause: err }); 
}

Try it yourself

JavaScript await import

JavaScript modules can now wait for the required resources to be imported 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;

From April 2021, class field declarations are supported in all modern browsers:

JavaScript private metoder og felter

class Hello {
  #counter = 0;  // Privat felt
  #myMethod() {} // Privat metode
}
const myClass = new Hello();
let x = myClass.#counter; // Fejl
myClass.#myMethod();      // Fejl

Fra juni 2021 er private metoder og felter understøttet i alle moderne browsere: