Promise.withResolvers() polyfill

promise-with-resolvers-polyfill.js

if (typeof Promise.withResolvers === 'undefined') {
  Promise.withResolvers = function () {
    let resolve, reject
    const promise = new Promise((res, rej) => {
      resolve = res
      reject = rej
    })
    return { promise, resolve, reject }
  }
}

// Usage:
// const { promise, resolve, reject } = Promise.withResolvers()
// console.log(promise, resolve, reject) // Promise { <pending> } [Function (anonymous)] [Function (anonymous)]
// ... Do something async and then call resolve or reject!