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ECMAScript 2018

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The JavaScript naming convention started with ES1, ES2, ES3, ES5 and ES6.

But, ECMAScript 2016 and ECMAScript 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
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