New Features in JavaScript 2020
| Col 1 | Col 2 |
|---|---|
| Feature | Description |
| BigInt | Stores values too big to store in a JavaScript number |
| String matchAll() | Searchs for all occurrences of a string in a string |
| Promise.allSettled() | Takes promises as input and returns a single promise |
| Dynamic Import | Loads JavaScript modules at runtime |
| globalThis | Refers to the global object independent of code environment |
| import.meta | Returns an object indicating the base URL of a module |
| Namespace Exports | Export a full namespace from a module without having to import it first |
New JavaScript Operators in 2020
| Col 1 | Col 2 | Col 3 |
|---|---|---|
| Oper | Description | |
| ?? | Nullish coalescing returns the first argument not nullish | |
| ?. | Optional chaining returns undefined if an object is undefined or null | |
| &&= | Logical AND assignment assigns the second value if the first value is true | |
| ||= | Logical OR assignment assigns the second value if the first value is false | |
| ??= | Nullish coalescing assignment assigns the second value if the first value is undefined or null |
Browser Support
ECMAScript 2020 is supported in all modern browsers since April 2021.
JavaScript BigInt
JavaScript BigInt variables are used to store big integer values that are too big to be represented by a a normal JavaScript Number.
JavaScript integers are only accurate up to about 15 digits.
Integer Example
let x = 999999999999999;
let y = 9999999999999999; // too big
To create a BigInt, append n to the end of an integer or call BigInt():
Example
let x = 1234567890123456789012345n;
let y = BigInt(1234567890123456789012345)
The JavaScript typeof a BigInt is "bigint":
Example
let x = BigInt(999999999999999);
let type = typeof x;
JavaScript String matchAll()
Before ES2020 there was no string method that could be used to search for all occurrences of a string in a string.
Example
const iterator = text.matchAll("Cats");
If the parameter is a regular expression, the global flag (g) must be set set, otherwise a TypeError is thrown.
Example
const iterator = text.matchAll(/Cats/g);
If you want to search case insensitive, the insensitive flag (i) must be set:
Example
const iterator = text.matchAll(/Cats/gi);
Note: ES2021 introduced the string method replaceAll().
The Nullish Coalescing Operator (??)
The ?? operator returns the first operand if it is not nullish. Otherwise it returns the second.
The ?? operator returns the second operand if the first operand is nullish.
Nullish is a word for describing null or undefined.
The ?? operator is used to provide default values and is distinct from the logical OR operator || because it only treats null and undefined as "nullish" and ignores other "falsy" values like 0 or an empty string.
Example
let name = null;
let text = "missing";
let result = name ?? text;
The Optional Chaining Operator (?.)
The Optional Chaining Operator returns undefined if an object property is undefined or null (instead of throwing an error).
Example
const car = {type:"Fiat", model:"500", color:"white"};
let name = car?.name;
Optional chaining not only works on object properties, but also on function calls and arrays.
Function Calls
| Col 1 | Col 2 | Col 3 |
|---|---|---|
| Use Case | Syntax | Behavior |
| Safe function call | obj.method?.() | Returns undefined if method does not exist |
| Return handling | let x = fn?.() | x is undefined if fn does not exist |
Arrays
| Col 1 | Col 2 | Col 3 |
|---|---|---|
| Use Case | Syntax | Returns |
| Safe element access | arr?.[2] | undefined if arr is null or undefined |
| Safe property on element | arr?.[1]?.name | Returns undefined safely |
| Safe method call | arr?.map(fn) | Returns undefined if arr does not exist |
| Default value fallback | arr?.[0] ?? "N/A" | Returns "N/A" if arr or element is missing |
The &&= Operator
The Logical AND Assignment Operator is used between two values.
If the first value is true, the second value is assigned.
Logical AND Assignment Example
let x = 10;
x &&= 5;
The ||= Operator
The Logical OR Assignment Operator is used between two values.
If the first value is false, the second value is assigned.
Logical OR Assignment Example
let x = 10;
x ||= 5;
The ??= Operator
The Nullish Coalescing Assignment Operator is used between two values.
If the first value is undefined or null, the second value is assigned.
Nullish Coalescing Assignment Example
let x;
x ??= 10;
JavaScript Promise.allSettled()
The Promise.allSettled() method returns a single Promise from a list of promises.
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");
});
// Settle All
Promise.allSettled([myPromise1, myPromise2]).then((results) =>
results.forEach((x) => myDisplay(x.status)),
);
Note: Promise.allSettled() means "Just run all promises. I don't care about the results".
JavaScript Dynamic Import
Dynamic Import is a way to load JavaScript modules at runtime, rather than at the start of your program.
Syntax
import("./module.js")
- The argument must be a string or expression that resolves to a path
- You must run the import inside a module script (
JS 2020 – FAQs
Quick answers about learning JS 2020 in JavaScript.
This free note from CodingNow 2.0 explains JS 2020 in JavaScript — concept, syntax and worked code examples you can copy, run and revise before interviews.Yes. Every JavaScript topic on CodingNow 2.0, including JS 2020, is 100% free with no signup required.With focused practice, most students grasp JS 2020 in 1–3 days from these notes; pairing it with CodingNow 2.0's mentor-led course takes you to job-ready depth faster.Use the code examples in this note, then ask doubts for free on the CodingNow 2.0 Community (/community) — expert instructors answer within 24 hours.
