New Features in JavaScript 2021
| Col 1 | Col 2 | Col 3 | Col 4 |
|---|---|---|---|
| Feature | Description | ||
| Promise.any() | Takes promises as input and returns a single promise | ||
| String replaceAll() | Replaces all occurrences of a substring in a string | ||
| Numeric Separator | New numeric separator (_) makes numbers more readable |
Browser Support
ECMAScript 2021 is supported in all modern browsers since April 2021:
JavaScript Promise.any()
Promise.any() is a static method in JavaScript that takes an iterable of Promises as input and returns a single Promise.
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");
});
// Run when any promise fulfill
Promise.any([myPromise1, myPromise2]).then((x) => {
myDisplay(x);
});
JavaScript String ReplaceAll()
ES2021 introduced the string method replaceAll():
Example
text = text.replaceAll("Cats","Dogs");
text = text.replaceAll("cats","dogs");
The replaceAll() method allows you to specify a regular expression instead of a string to be replaced.
If the parameter is a regular expression, the global flag (g) must be set, otherwise a TypeError is thrown.
Example
text = text.replaceAll(/Cats/g,"Dogs");
text = text.replaceAll(/cats/g,"dogs");
Note: ES2020 introduced the string method matchAll().
JavaScript Numeric Separator (_)
ES2021 intoduced the numeric separator (_) to make numbers more readable:
Example
const num = 1_000_000_000;
The numeric separator is only for visual use.
Example
const num1 = 1_000_000_000;
const num2 = 1000000000;
(num1 === num2);
The numeric separator can be placed anywhere in a number:
Example
const num1 = 1_2_3_4_5;
Note: The numeric separator is not allowed at the beginning or at the end of a number. In JavaScript only variables can start with _.
