.race()

Returns the first Promise in an iterableObject that is either resolved or rejected.

Syntax

Promise.race(iterableObject);

Example #1

If the iterableObject is empty, then the returned Promise will be in “pending” forever and never resolve.

const emptyPromises = [];
Promise.race(emptyPromises).then((result) => {
console.log(result); // Nothing logged to the console
});

Example #2

In the spirit of a race, ssing setTimeout() within two runners named runnerA and runnerB:

const runnerA = new Promise((resolve, reject) => {
setTimeout(reject, 100, 'The winner is runnerA!');
});
const runnerB = new Promise((resolve, reject) => {
setTimeout(resolve, 300, 'The winner is runnerB!');
});
const promises = [runnerA, runnerB];
Promise.race(promises)
.then((result) => {
console.log(result);
})
.catch((err) => {
console.log(err);
})
.finally(() => {
console.log('Operations for Promise.race() have finished.');
});

Contributors

Interested in helping build Docs? Read the Contribution Guide or share your thoughts in this feedback form.

Learn JavaScript on Codecademy

Contributors