Cancelable Promise

cancelable-promise.js

export class CanceledError extends Error {
  constructor (promise) {
    super()

    if (Error.captureStackTrace) {
      Error.captureStackTrace(this, CanceledError)
    }

    this.promise = promise
    this.isCanceled = true
  }
}

/**
* Make a Promise cancelable.
*
* Example:
*
* let cancelablePromise = new CancelablePromise(
*   api.get('/foo')
* )
* cancelablePromise
*   .promise
*   .then((results) => console.log(results))
*   .catch((error) => {
*     if (!error.isCanceled) {
*       console.log('Something went wrong.')
*     } else {
*       console.log('Promise canceled!')
*     }
*   })
*
* cancelablePromise.cancel()
* // "Promise canceled!"
*
*/
export class CancelablePromise {
  constructor (promise) {
    this.isCanceled = false
    // Wrap original Promise in a new Promise.
    this.promise = new Promise((resolve, reject) => {
      promise.then(
        (value) => {
          if (this.isCanceled) {
            reject(new CanceledError(promise))
          } else {
            resolve(value)
          }
        },
        (error) => {
          if (this.isCanceled) {
            reject(new CanceledError(promise))
          } else {
            reject(error)
          }
        }
      )
    })
  }

  cancel () {
    this.isCanceled = true
  }
}

export default CancelablePromise