In this Hasty Treat, Scott and Wes talk about seven new JavaScript proposals — what they do, where they’re at, and how you might use them.

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Show Notes

03:32 - Seven new JavaScript proposals

• https://github.com/tc39/proposals

06:25 - JSON Modules

• https://github.com/tc39/proposal-json-modules

Builds on the import assertions

No named exports

Not executed, to avoid security issues

Not in Node yet

09:55 - Array Find From Last

• https://github.com/tc39/proposal-array-find-from-last

The problem: you need to group together async code.The only way to do that right now is to wrap it in a function.

11:40 - Async Do

• https://github.com/tc39/proposal-async-do-expressions

Async do will allow you to group together a block of code and mark it as async.

No need for an iife

Downside to this is that it’s a code block, so if you need to return any values, you’ll need to jump that up a scope level.

Promise.all([ async do { let result = await fetch('thing A'); await result.json(); }, async do { let result = await fetch('thing B'); await result.json(); }, ]).then(([a, b]) => console.log([a, b]));

14:33 - Change Array By Copy

• https://github.com/tc39/proposal-change-array-by-copy

Like old array methods, but returns a new array rather than mutating

17:48 - Temporal

• https://github.com/tc39/proposal-temporal

Stage 3, looking good!

Amazing, large, very good Date API

Syntax 295: Hasty Treat — Temporal Date Objects in JavaScript

18:35 - As Patterns

• https://github.com/zkat/proposal-as-patterns

Scott don’t get it

Stage 0

when ([ ‘go’, (‘north’ | ‘east’ | ‘south’ | ‘west’) as dir ]) { … }

20:47 - Pattern Matching

• https://github.com/tc39/proposal-pattern-matching

VERY Rust-like

• https://doc.rust-lang.org/1.6.0/book/patterns.html

Stage 1

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