JavaScript ECMAScript 2021
JavaScript Version Numbers
Old ECMAScript versions was named by numbers: ES5 and ES6.
From 2016, versions are named by year: ES2016, 2018, 2020 ...
New Features in ES2021
Warning
These features are relatively new.
Older browsers may need an alternative code (Polyfill)
JavaScript Promise.any()
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);
});
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Promise.any() is supported in all modern browsers since September 2020:
| Chrome 85 | Edge 85 | Firefox 79 | Safari 14 | Opera 71 |
| Aug 2019 | Aug 2020 | Jul 2020 | Sep 2020 | Sep 2020 |
JavaScript String ReplaceAll()
ES2021 introduced the string method replaceAll():
Example
text = text.replaceAll("Cats","Dogs");
text = text.replaceAll("cats","dogs");
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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");
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Note
ES2020 introduced the string method matchAll().
JavaScript Numeric Separator (_)
ES2021 intoduced the numeric separator (_) to make numbers more readable:
The numeric separator is only for visual use.
The numeric separator can be placed anywhere in a number:
Note
The numeric separator is not allowed at the beginning or at the end of a number.
In JavaScript only variables can start with _.
The numeric separator is supported in all modern browsers since January 2020:
| Chrome 75 | Edge 79 | Firefox 74 | Safari 13.1 | Opera 67 |
| Jun 2019 | Jan 2020 | Oct 2019 | Sep 2019 | Jun 2019 |