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How TypeScript 3.7 Helps Quality

Matt Eland on November 07, 2019

In this article I’ll go over a few key highlights from the recent release of TypeScript 3.7. I’ll be looking at things through the lens of how they...

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Afief S • Nov 7 '19

Does "Uncalled function check" has wrong screenshot? Because the screenshot show "declare" error instead of uncalled function check

Matt Eland • Nov 7 '19

Yeah... I think I cropped it to the wrong error. It should have read: This condition will always return true since the function is always defined. Did you mean to call it instead?

I've made the edit.

I feel shame. Don't publish tired.

Pulkit Kashyap • Nov 7 '19

I think some of the examples are not in the right order. Nice otherwise :)

Matt Eland • Nov 7 '19

As in you'd like to see the functions reordered within the gists for readability?

Pulkit Kashyap • Nov 7 '19

Ya kind of

Pierre Salaün • Nov 7 '19 • Edited

The gists don’t seem to be in the right order, as some of them don’t match the text surrounding them.

boredcity • Nov 7 '19

example for Nullish Coalescing doesn't really seem to explain why it's useful: "old way" would just be var calculator = someCalculator || new Calculator();

Danijel Vincijanović • Nov 7 '19 • Edited

I was also wondering what's the difference between those two and I've found it. Nullish Coalescing better handles cases when it comes to truthy/falsy values.

For example:

const a = 0
const b = a || 100

console.log(b) // 100

Same thing, but different result with Nullish Coalescing:

const a = 0
const b = a ?? 100

console.log(b) // 0

Matt Eland • Nov 8 '19

I personally hate the use of the || operator in this context, but that's mostly because my background is a C# one where I read the operator and think that b would be assigned to true since a and 100 would both be evaluated as booleans.

Obviously they wouldn't, but to me ?? is way more intuitive than the use of || in this context.

boredcity • Nov 7 '19

I thought I remembered something like this being the edge case where this was useful... Thank you, this seems like a better example!

Abraham Schilling • Nov 7 '19

Yessss I've been waiting for Optional Chaining and Nullish Coalescing so hard, thanks for writing this up and appearing on my newsfeed 🙌

Matt Eland • Nov 8 '19

I know. Almost every merge request I review in the JavaScript / TypeScript world I wish the committer had access to optional chaining.

Bnaya Peretz • Nov 8 '19

The decalre keyword is not really a feature, but compatebility option with es class members
devblogs.microsoft.com/typescript/...

Pragmatic Maciej • Nov 8 '19 • Edited

Some more details about why optional chaining is not so perfect thing
dev.to/macsikora/what-is-wrong-wit...