Returning data from promise to a variable using map

Question

I want to return the data to a variable. I have resolved the promise and making it print to console. I want that the data should be access outside and can be used by a variable. I want whatever values are there in console.log(x) , should come outside the loop in a variable ( say variable name z)

 var libobj =await service.getdata(); //----------> returning from service file and libobj is returning  promise (fullfilled)

// var z; -----Data needed here or below the map loop

libobj.map( (res: any) => 
(res.then((x : any )=>console.log(x)) )); //--------> console .log(x) printing all  the data needed

don't know what "getdata()" returns, but if it is fetch call it need to be "libobj.json()" — Jafar Jabr, Jan 21 '22 at 08:20
Check [Promise.all](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all). — Nalin Ranjan, Jan 21 '22 at 09:07
`let values = []; (async () => values = await Promise.all(libobj);)()`, something along those lines. A better example can be produced if you can come-up with a value for `libobj`, a value suitable to run the test. — Nalin Ranjan, Jan 21 '22 at 09:09
@NalinRanjan The code you wrote won't work (see https://stackoverflow.com/q/23667086/8376184). Instead, you can do `const values = await Promise.all(libobj)` — FZs, Jan 21 '22 at 09:31
Thanks @FZs, I have updated. Also, it's merely an example for the OP to see how can he use `Promise.all`... — Nalin Ranjan, Jan 21 '22 at 09:37

Nalin Ranjan · Answer 1 · 2022-01-21T09:36:47.883

-1

Following is an example to showcase Promise.all...

let createAPromise = (x) => new Promise((res, rej) => setTimeout(() => { console.log(`Resolving ${x}`); res(x)}, x));


async function test() {

  const libobj = [300, 500, 700].map(x => createAPromise(x));

  const values = await Promise.all(libobj);

  console.log('Resolved all with', values);
}

test();

This example is only to highlight a way of Promise.all to obtain a final value from a collection of promises...

edited Jan 21 '22 at 09:36

answered Jan 21 '22 at 09:19

Nalin Ranjan

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I replied to your comment (I didn't notice your answer). The point I was trying to make there was that assigning an external value from a `.then` callback doesn't work, but I see that your answer didn't have this problem. :) `let` or `const` makes little difference here. – FZs Jan 21 '22 at 10:05

Returning data from promise to a variable using map

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