Way to have cancelable promise

cancelable-promise.js

// @flow

// https://facebook.github.io/react/blog/2015/12/16/ismounted-antipattern.html

export type CancelablePromise = {
  promise: Promise<any>,
  cancel: Function,
}

export const makeCancelablePromise = (
  promise: Promise<*>
): CancelablePromise => {
  let hasCanceled = false

  const wrappedPromise: any = new Promise((resolve, reject) => {
    promise.then((val) =>
      hasCanceled ? reject({ isCanceled: true }) : resolve(val)
    )
    promise.catch((error) =>
      hasCanceled ? reject({ isCanceled: true }) : reject(error)
    )
  })

  return {
    promise: wrappedPromise,
    cancel(): void {
      hasCanceled = true
    },
  }
}

export const cancelableResolve = (data: any) : CancelablePromise => {
  return makeCancelablePromise(Promise.resolve(data))
}

export const cancelableReject = (data: any) : CancelablePromise => {
  return makeCancelablePromise(Promise.resolve(data))
}

export default (
  promise: Promise<any>,
  resolve: (data: any) => void,
  reject: (error: string) => void
): CancelablePromise => {
  const cancelablePromise = makeCancelablePromise(promise)
  cancelablePromise.promise
  .then((response) => {
    resolve(response.json)
  })
  .catch((result) => {
    const { isCanceled, error } = result
    if (isCanceled) {
      return
    }
    reject(error || result)
  })

  return cancelablePromise
}

const cp = cancelablePromise(fetch(), reject, resolve)
cp.cancel()