JavaScript 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
- Array at()
- String at()
- RegExp /d
- Object.hasOwn()
- error.cause
- await import
- Class field declarations
- Private methods and fields
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 = "Schoolsw3";
let letter = name.at(2);
Try it Yourself »
Get the third letter of name:
const name = "Schoolsw3";
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.
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.
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 |