codekingpro/portable-devtools

1'use strict';2 3import CanceledError from './CanceledError.js';4 5/**6 * A `CancelToken` is an object that can be used to request cancellation of an operation.7 *8 * @param {Function} executor The executor function.9 *10 * @returns {CancelToken}11 */12class CancelToken {13  constructor(executor) {14    if (typeof executor !== 'function') {15      throw new TypeError('executor must be a function.');16    }17 18    let resolvePromise;19 20    this.promise = new Promise(function promiseExecutor(resolve) {21      resolvePromise = resolve;22    });23 24    const token = this;25 26    // eslint-disable-next-line func-names27    this.promise.then(cancel => {28      if (!token._listeners) return;29 30      let i = token._listeners.length;31 32      while (i-- > 0) {33        token._listeners[i](cancel);34      }35      token._listeners = null;36    });37 38    // eslint-disable-next-line func-names39    this.promise.then = onfulfilled => {40      let _resolve;41      // eslint-disable-next-line func-names42      const promise = new Promise(resolve => {43        token.subscribe(resolve);44        _resolve = resolve;45      }).then(onfulfilled);46 47      promise.cancel = function reject() {48        token.unsubscribe(_resolve);49      };50 51      return promise;52    };53 54    executor(function cancel(message, config, request) {55      if (token.reason) {56        // Cancellation has already been requested57        return;58      }59 60      token.reason = new CanceledError(message, config, request);61      resolvePromise(token.reason);62    });63  }64 65  /**66   * Throws a `CanceledError` if cancellation has been requested.67   */68  throwIfRequested() {69    if (this.reason) {70      throw this.reason;71    }72  }73 74  /**75   * Subscribe to the cancel signal76   */77 78  subscribe(listener) {79    if (this.reason) {80      listener(this.reason);81      return;82    }83 84    if (this._listeners) {85      this._listeners.push(listener);86    } else {87      this._listeners = [listener];88    }89  }90 91  /**92   * Unsubscribe from the cancel signal93   */94 95  unsubscribe(listener) {96    if (!this._listeners) {97      return;98    }99    const index = this._listeners.indexOf(listener);100    if (index !== -1) {101      this._listeners.splice(index, 1);102    }103  }104 105  /**106   * Returns an object that contains a new `CancelToken` and a function that, when called,107   * cancels the `CancelToken`.108   */109  static source() {110    let cancel;111    const token = new CancelToken(function executor(c) {112      cancel = c;113    });114    return {115      token,116      cancel117    };118  }119}120 121export default CancelToken;122