ECMAScript 2021 (JS 2021/2022)

JavaScript in 2021/2022 continues to evolve, with ES2021/ES2022 bringing enhanced features like private class fields, promise improvements, and record data structures, boosting developer productivity and code quality.

JavaScript New Features in ES2021

Name	Description
Promise any():	Resolves if any Promise resolves, else reject after all reject.
String replaceAll()	Replaces all occurrences of a substring with another in string
Numeric Separators (_)	separating digits in numbers using underscores.

JavaScript in 2022 new features :

Name	Description
Array at()	Retrieves element at index supports positive and negative indexing
String at()	Finds character at index, supports positive and negative indexing
RegExp /d	Matches any digit (0-9) in a regular expression pattern.
Object.hasOwn()	Checks if object has its own specified property.
error.cause	Accesses the cause of an error in the error object.
await import	Awaits and imports a module dynamically in JavaScript code asynchronously.
Private methods and fields	Encapsulates data with restricted access using private methods and fields.
Class field declarations	Defines class properties directly without constructor using concise syntax.

We will explore all the above methods along with their basic implementation with the help of examples.

Method 1: Promise any()

Promise.any() is a JavaScript ES2021/ES2022 method that takes an array of Promises and returns the first resolved Promise, rejecting only if all Promises reject.

Syntax:

Promise.any(iter)

Example: This example, shows the basic use of Promise.any() method.

Javascript

let prom1 = new Promise((resolve, reject) => {
    reject("Failure");
})
let prom2 = new Promise((resolve, reject) => {
    reject("Failed to load");
})
let prom3 = new Promise((resolve, reject) => {
    resolve("Worked");
})
let prom4 = new Promise((resolve, reject) => {
    resolve("Successful");
})

let prom = [prom1, prom2, prom3, prom4];

Promise.any(prom).then((val) => { console.log(val) });

Output

Worked

Method 2: String replaceAll()

String replaceAll() is a JavaScript method (ES2021/ES2022) replacing all occurrences of a substring with another, returning a new string.

Syntax:

const newString = originalString.replaceAll(regexp | substr , newSubstr | function)

Example: Below is an example of the String replaceAll() Method.

Javascript

function gfg() {
    let string = "Geeks or Geeks";
    newString = string.replaceAll("or", "for");
    console.log(newString);
}
gfg();

Output

Geeks for Geeks

Method 3: Numeric Separators (_)

Numeric Separators (_) in JavaScript (ES2021/ES2022) allow improved readability by placing underscores as visual separators in large numbers for better code comprehension.

Syntax:

let num1 = 1_000_000_000;

Example: Here is the basic example of above method.

Javascript

let num1 = 1_000_000_000;
let num2 = 1000000000;
console.log(num1 === num2);

Output

true

Method 4: Array at()

The JavaScript Array at() method takes an integer value (index) as a parameter and returns the element of that index. It allows positive and negative integers. For the negative integer, it counts back from the last element in the array.

Syntax:

at(index);

Example: This code shows the value extracted at the given index.

Javascript

const arr = [45, 32, 69, 21];
const index = 3;

console.log(arr.at(index));

Output

21

Method 5: String at()

String.at() finds character at specified index, supports positive and negative indexes. Positive indexes start from array start, negative from end.

Syntax:

let a = str.at(ind);

Example: In this example, we will use the String.at() method with a positive index.

Javascript

let str1 = "Welcome to GeeksforGeeks";
let str2 = "GeeksforGeeks";
console.log(str1.at(3));
console.log(str2.at(8))

Output

c
G

Method 6: RegExp \D

The RegExp \D Metacharacter in JavaScript is used to search non-digit characters i.e all the characters except digits. It is the same as [^0-9].

Syntax:

/\D/ 

Example: This example searches the non-digit characters in the whole string.

Javascript

function geek() {
    let str1 = "GeeksforGeeks@_123_$";
    let regex4 = /\D/g;
    let match4 = str1.match(regex4);

    console.log("Found " + match4.length
        + " matches: " + match4);
}
geek()

Output

Found 17 matches: G,e,e,k,s,f,o,r,G,e,e,k,s,@,_,_,$

Method 7: Object.hasOwn()

Object.hasOwn() is a method that checks if an object has a specific property directly on itself, returning true if found, else false.

Syntax:

Object.hasOwn(obj, prop)

Example: This example uses the hasOwn() method to check if a property exists or not.

Javascript

let details = {
    name: "Raj",
    course: "DSA",
    website: "geeksforgeeks.org",
}

console.log(Object.hasOwn(details, 'name'));
console.log(Object.hasOwn(details, 'course'));
console.log(Object.hasOwn(details, 'phone number'));

Output

true
true
false

Supported browser:

• Chrome 1
• Edge 12
• Firefox 1
• Safari 1
• Opera 3