workbox-core/src/_private/Deferred.ts

This module is used by a number of the other Workbox modules to share common code.

/*
  Copyright 2018 Google LLC

  Use of this source code is governed by an MIT-style
  license that can be found in the LICENSE file or at
  https://opensource.org/licenses/MIT.
*/

import '../_version.js';

/**
 * The Deferred class composes Promises in a way that allows for them to be
 * resolved or rejected from outside the constructor. In most cases promises
 * should be used directly, but Deferreds can be necessary when the logic to
 * resolve a promise must be separate.
 *
 * @private
 */
class Deferred<T> {
  promise: Promise<T>;
  resolve!: (value: T) => void;
  reject!: (reason?: any) => void;

  /**
   * Creates a promise and exposes its resolve and reject functions as methods.
   */
  constructor() {
    this.promise = new Promise((resolve, reject) => {
      this.resolve = resolve;
      this.reject = reject;
    });
  }
}

export {Deferred};