Angular 5 wait for promises to return from for loop

Question

I have the array as below:

arr = ['res1', 'res2', 'res3'];

Then for each arr value, I will do an API call that will return a promise

arr.forEach(val => this.getPromise(val));

The method getPromise returns a promise. I need to wait for all promises before i invoke another method. How should I do it?

this moght be helpful https://daveceddia.com/waiting-for-promises-in-a-loop/ — Pratap A.K, Sep 26 '18 at 02:45
First try building an array of promises, then using [Promise.all(arrayOfPromises)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all) and see if that works for you. This way you can execute all in parallel. — Alexander Staroselsky, Sep 26 '18 at 02:50

score 4 · Accepted Answer · edited Sep 26 '18 at 03:12

You can use Promise.all() to perform an action after all promises have resolved. It takes an array of promises:

const promises = ["val1", "val2"].map(val => this.getPromise(val));

Promise.all(promises)
    .then(results => console.log(results)) // this is an array
    .catch(err => console.log(err));

You can use then() and catch() as you would with a promise. The response is an array of resolved values.

Hopefully that helps!

Angular 5 wait for promises to return from for loop

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