Could someone please explain what this could be used for ?
Pattern matching is very common in ML languages and is a core part of Rust.
As another commenter said, it's like conditionals on steroids.
JavaScript Pattern Matching Proposal
21–30 of 254 posts
Re: JavaScript Pattern Matching Proposal
#22Could someone please explain what this could be used for ?
Smooshes the evaluation of an object that can be many different shapes into an easy to understand operation. I think the HTTP response is a great example. It can have many status codes which can determine how you want to proceed with that response. If you've worked with handling HTTP responses, you've most likely implemented some version of a 'match' operation before.
> Smooshes the evaluation
I see what you did there...
Re: JavaScript Pattern Matching Proposal
#23Isn't pattern matching interesting only in a strongly typed environment where the compiler can statically check that you are giving instructions for all possible cases?
Re: JavaScript Pattern Matching Proposal
#24Javascript is such a mess, this proposal looks really bad, and the guys discussing it are saying things like: "we should make sure that this doesn't look like anything else, so that people who learn the language don't confuse match and switch..."
There is also a lot of "we shouldn't break that" messages, and people reply with "oh we already screwed that up here and there, so it's fine"...
Re: JavaScript Pattern Matching Proposal
#25What an ugly syntax. They should follow switch/case syntax for consistency.
Pattern matching doesn't work the same way as switch/case though. Using that syntax would be misleading and confusing.
Re: JavaScript Pattern Matching Proposal
#26Could someone please explain what this could be used for ?
Instead of using if or switch statements to compute a value, you can use a prettier interface.
So this:
function getStatus(status) {
if (status === 200){
return "Success";
} else if (status === 401){
return "Fail!";
}
}
var myString = getStatus(response.status);
var myString = match (status) {
{200} => "Success",
{401} => "Fail!"
}Re: JavaScript Pattern Matching Proposal
#27I really like this. The syntax looks a little weird at first, but it's actually a very nice complement to modern JavaScript's object destructing mechanism: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
Re: JavaScript Pattern Matching Proposal
#28Earlier quoted context omitted.
Smooshes the evaluation of an object that can be many different shapes into an easy to understand operation. I think the HTTP response is a great example. It can have many status codes which can determine how you want to proceed with that response. If you've worked with handling HTTP responses, you've most likely implemented some version of a 'match' operation before.
Is not `switch` enough for this?
It's more concise than switch, as well as more powerful (can destructure objects). You can't set things equal to the result of a switch. I find the pattern very convenient.
let day;
switch (date) {
case 1:
day = "mon";
break;
case 2:
day = "tues";
break;
default:
day = "wed";
break;
let day = match(date) {
1 => 'mon',
2 => 'tues'
}Re: JavaScript Pattern Matching Proposal
#29What an ugly syntax. They should follow switch/case syntax for consistency.
Let's see an example of your proposed alternative syntax.
Re: JavaScript Pattern Matching Proposal
#30Isn't pattern matching interesting only in a strongly typed environment where the compiler can statically check that you are giving instructions for all possible cases?
No, not at all. E.g. Erlang is built around pattern matching as a core feature even though it's an untyped language.