ECMAScript 2018
The JavaScript naming convention started with ES1, ES2, ES3, ES5 and ES6.
But, ECMAScript 2016 and 2017 was not called ES7 and ES8.
Since 2016 new versions are named by year (ECMAScript 2016 / 2017 / 2018).
New Features in ECMAScript 2018
This chapter introduces the new features in ECMAScript 2018:
JavaScript Asynchronous Iteration
ECMAScript 2018 added asynchronous iterators and iterables.
With asynchronous iterables, we can use the await
keyword in for/of loops.
Example
for await () {}
Firefox and Safari were the first browsers with support for JavaScript asynchronous iteration:
| Chrome 63 | Edge 79 | Firefox 57 | Safari 11 | Opera 50 |
| Dec 2017 | Jan 2020 | Nov 2017 | Sep 2017 | Jan 2018 |
JavaScript Promise.finally
ECMAScript 2018 finalizes the full implementation of the Promise object with Promise.finally:
Example
let myPromise = new Promise();
myPromise.then();
myPromise.catch();
myPromise.finally();
Chrome and Firefox were the first browsers with support for Promise.finally:
| Chrome 63 | Edge 18 | Firefox 58 | Safari 11.1 | Opera 50 |
| Dec 2017 | Nov 2018 | Jan 2018 | Mar 2018 | Jan 2018 |
JavaScript Object Rest Properties
ECMAScript 2018 added rest properties.
This allows us to destruct an object and collect the leftovers onto a new object:
Example
let { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
x; // 1
y; // 2
z; // { a: 3, b: 4 }
Chrome, Firefox, ans Opera were the first browsers with support for object rest properties:
| Chrome 60 | Edge 79 | Firefox 55 | Safari 11.1 | Opera 47 |
| Jul 2017 | Jan 2020 | Aug 2017 | Mar 2018 | Aug 2017 |
New JavaScript RegExp Features
ECMAScript 2018 added 4 new RegExp features:
- Unicode Property Escapes (\p{...})
- Lookbehind Assertions (?<= ) and (?<! )
- Named Capture Groups
- s (dotAll) Flag
Chrome and Firefox were the first browsers with support for all the new RegExp features:
| Chrome 64 | Edge 79 | Firefox 78 | Safari 12 | Opera 51 |
| Jan 2018 | Jan 2020 | Jun 2020 | Sep 2018 | Feb 2018 |
