Hasty Treat - Seven Interesting JavaScript Proposals - Async Do, JSON Modules, Immutable Array Methods, and More!

Jun 28, 2021

Discover the latest buzz in JavaScript with discussions on seven intriguing proposals. Learn about JSON modules and how they promise smoother imports. Explore the concept of immutable array methods for safer coding practices. Dive into the async do feature that groups async code more elegantly, eliminating the need for IIFEs. There’s also a look at Array Find From Last, which addresses common code challenges. Plus, hear about future advancements like enhanced destructuring patterns that could change how coding is done!

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INSIGHT

JSON Modules

JSON modules allow importing JSON data directly into JavaScript without transpilation.
This simplifies data handling and improves security by preventing code execution within JSON files.

INSIGHT

Array Find From Last

findLast and findLastIndex methods efficiently search arrays from the end.
This avoids unnecessary array copying and reversal, improving performance.

INSIGHT

Async Do

Async do expressions provide a concise way to group asynchronous code within a block.
This simplifies awaiting tasks without defining separate async functions or using IIFEs.

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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

{props => match (props) { when ({ loading }) { ; } when ({ error }) { ; } when ({ data }) { ; } }} Tweet us your tasty treats!

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