Promise.all()

The Promise.all(iterable) method returns a promise that resolves when all of the promises in the iterable argument have resolved, or rejects with the reason of the first passed promise that rejects.

Syntax

Promise.all(iterable);

Parameters

iterable

An iterable object, such as an Array. See iterable.

Return value

A Promise that resolves when all of the promises in the given iterable have resolved, or rejects if any of the promises rejects.

Description

Promise.all passes an array of values from all the promises in the iterable object that it was passed. The array of values maintains the order of the original iterable object, not the order that the promises were resolved in. If something passed in the iterable array is not a promise, it's converted to one by Promise.resolve. 

If any of the passed in promises rejects, the all Promise immediately rejects with the value of the promise that rejected, discarding all the other promises whether or not they have resolved. If an empty array is passed, then this method resolves immediately.

Examples

Using Promise.all

Promise.all waits for all fulfillments (or the first rejection).

var p1 = Promise.resolve(3);
var p2 = 1337;
var p3 = new Promise((resolve, reject) => {
  setTimeout(resolve, 100, "foo");
}); 

Promise.all([p1, p2, p3]).then(values => { 
  console.log(values); // [3, 1337, "foo"] 
});

Promise.all fail-fast behaviour

Promise.all is rejected if one of the elements is rejected and Promise.all fails fast: If you have four promises which resolve after a timeout, and one rejects immediately, then Promise.all rejects immediately.

var p1 = new Promise((resolve, reject) => { 
  setTimeout(resolve, 1000, "one"); 
}); 
var p2 = new Promise((resolve, reject) => { 
  setTimeout(resolve, 2000, "two"); 
});
var p3 = new Promise((resolve, reject) => {
  setTimeout(resolve, 3000, "three");
});
var p4 = new Promise((resolve, reject) => {
  setTimeout(resolve, 4000, "four");
});
var p5 = new Promise((resolve, reject) => {
  reject("reject");
});

Promise.all([p1, p2, p3, p4, p5]).then(values => { 
  console.log(values);
}, reason => {
  console.log(reason)
});

//From console:
//"reject"

Specifications

Browser compatibility

To contribute to this compatibility data, please write a pull request against this file: https://github.com/mdn/browser-compat-data/blob/master/javascript/promise.json.

See also

• Promise
• Promise.race()