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);

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

If any of the passed in promises rejects, the all Promise immediately rejects with the value of the promise that rejected, ignoring all the other promises whether or not they have resolved. If an empty array is passed, then this method resolves immediately. If the returned promise fulfills, it is fulfilled with an array of the values from the fulfilled promises in the same order as defined in the iterable. If the returned promise rejects, it is rejected with the reason from the first promise in the iterable that rejected. This method can be useful for aggregating results of multiple promises.

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"

//It's even possible to use .catch
Promise.all([p1, p2, p3, p4, p5]).then(values => { 
  console.log(values);
}).catch(reason => { 
  console.log(reason)
});

//From console: 
//"reject"

Specifications

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Promise.all' in that specification.	Standard	Initial definition in an ECMA standard.
ECMAScript 2017 Draft (ECMA-262) The definition of 'Promise.all' in that specification.	Draft

Browser compatibility

See also

• Promise
• Promise.race()