I was googling, but cannot find the information what and how should I add to my project to allow me using ES6 methods like Array.from
__ EDIT: removed prototype word
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1'Array.from' is supported in most browsers, but you can find a polyfill in MDNNitzan Tomer– Nitzan Tomer2016-04-19 09:33:33 +00:00Commented Apr 19, 2016 at 9:33
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2The question is how to add it to TypeScript definitions... I don't need polyfill, I use Babel and TypeScript to translate my ES6 code to ES5. Just TypeScript has no definition, for newest methods...Isla– Isla2016-04-19 13:15:18 +00:00Commented Apr 19, 2016 at 13:15
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4 Answers
If you are sure the API exists on your engine at runtime, compile with --lib es6 (or --lib dom,es6 if you are using the DOM APIs).
See Compiler Options documentation for more details.
1 Comment
vandijkstef
Please remove the space to make it like this '--lib dom,es6'.
You can easily extend existing types like so:
interface Array {
from(arrayLike: any, mapFn?, thisArg?): Array<any>;
}
The problem here is that this will add the function to the array instances and not as a static function like you require.
But that can be done like so:
interface ArrayConstructor {
from(arrayLike: any, mapFn?, thisArg?): Array<any>;
}
Then you should be able to use Array.from.
Try it out on Playground.
Edit
If you need to polyfill the implementation (because the environment in which you intend to run doesn't have it), then this is how:
interface ArrayConstructor {
from(arrayLike: any, mapFn?, thisArg?): Array<any>;
}
Array.from = function(arrayLike: any, mapFn?, thisArg?): Array<any> {
// place code from MDN here
}
2nd edit
Based on a comment, I'm adding a typed version:
interface ArrayConstructor {
from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): Array<U>;
from<T>(arrayLike: ArrayLike<T>): Array<T>;
}
It's an exact copy of how it's defined in the lib.es6.d.ts.
19 Comments
Isla
Does it mean that there is no "standard" way of adding ES6 methods definitions to TS? I tried to find it here: definitelytyped.org/tsd but without any luck... Is this next "great" thing, made by MS?
Nitzan Tomer
@Kania What's not standard about it? The language gives you the ability to add methods when needed, what else can you ask for?
Isla
ES6 is not a private project. Why should I add defined by ES6 methods manually? maybe I expect too much from MS.
Nitzan Tomer
There are quite a few things that people would like to be added to typescript, and things are done over time, but you can't expect it to have it all.. But since you can very easily add it yourself, maybe it's not on their top priorities
Nitzan Tomer
@SandyGifford My bad, I forgot to copy the other signature for it (which doesn't include the mapping). I fixed my answer.
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I hope it isnt terribly off topic but I found this while refactoring js to ts, and if you have an array like, it appears to work simply passing the array like to the constructor instead of using from, removing the need for the extra method.
eg
// someScript.js
Array.from( arrayLikeThing );
becomes
// someScript.ts
Array( arrayLikeThing );
If there are other reasons to maintain using .from then the above answers are great.
3 Comments
Vincent Buscarello
As a warning, just found out this doesnt compile to array.from, so may be best to jsut reimplement like above
dimpiax
Array.from(Array(3)).map(v => 1) // [1, 1, 1]dimpiax
Array(Array(3)).map(v => 1) // [1]added below line to tsconfig.json inside compilerOptions solved for me.
"lib": [ "DOM", "ES2015.Core", "DOM.Iterable", "ES2015.Collection", "ES2015.Iterable", "ES2015" ]
