How does promise.all work?

Question

I started diggin\' in promises and found interesting Promise.all.

It is stated in MDN that

The Promise.all(iterable) method returns a promise

Answer 1

The Promise.all(iterables) function returns a single Promise.Here we provide multiple Promises as argument. Promise.all(iterables) function returns promise only when all the promises (argument) have resolved. It rejects when first promise argument reject.

var promise1 = Promise.resolve(3);
var promise2 = 42;
var promise3 = new Promise(function(resolve, reject) {
  setTimeout(resolve, 100, 'foo');
});

Promise.all([promise1, promise2, promise3]).then(function(values) {
  console.log(values);
// expected output: Array [3, 42, "foo"]
});

Syntax:

Promise.all(func1, func2 [,funcN])

Parameters:

Read more at - https://www.oodlestechnologies.com/blogs/An-Introduction-To-Promise.all-Function