9.6 JS 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
Des 2017	Jan 2020	Nov 2017	Sep 2017	Jan 2018

JavaScript Promise.finally

ECMAScript 2018 finalizes the full implermentation 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
Des 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