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| // Use a polyfill to make it useable in old browswers | |
| import 'abortcontroller-polyfill/dist/abortcontroller-polyfill-only'; | |
| // When abort happens, this error will be throw | |
| export class AbortError extends Error { | |
| constructor(message: string = 'Aborted') { | |
| super(message); | |
| this.name = 'AbortError'; | |
| } | |
| } | |
| // General interface of Abortable | |
| export interface Abortable { | |
| abort: (reason?: string) => void; | |
| readonly abortReason?: string; | |
| } | |
| // The executor function should be passed to the constructor when create a Promise | |
| interface ExecutorFunction<T> { | |
| (resolve: (value?: PromiseLike<T> | T) => void, reject: (reason?: any) => void): void; | |
| } | |
| // The executor function should be passed to the constructor when create a AbortablePromise | |
| interface AbortableExecutorFunction<T> { | |
| (resolve: (value?: PromiseLike<T> | T) => void, reject: (reason?: any) => void, abortSignal: AbortSignal): void; | |
| } | |
| // AbortablePromise is a subclass of Promise that implements Abortable interface | |
| export class AbortablePromise<T> extends Promise<T> implements Abortable { | |
| // Method defination `.abort()` | |
| public abort: Abortable['abort']; | |
| // Getter to access abort reason | |
| public get abortReason(): string | undefined { | |
| return this._abortReason; | |
| } | |
| // Internal store of abort reason | |
| private _abortReason?: string; | |
| // Constructor, note we can provide 3 args: resolve, reject, abortSignal | |
| constructor(executor: AbortableExecutorFunction<T>) { | |
| const abortController = new AbortController(); | |
| const abortSignal = abortController.signal; | |
| // This is the executor function to be passsed to the superclass - Promise | |
| const normalExecutor: ExecutorFunction<T> = (resolve, reject) => { | |
| abortSignal.addEventListener('abort', () => { | |
| reject(new AbortError(this.abortReason)); | |
| }); | |
| executor(resolve, reject, abortSignal); | |
| }; | |
| super(normalExecutor); | |
| // Bind the abort method | |
| this.abort = reason => { | |
| this._abortReason = reason ? reason : 'Aborted'; | |
| abortController.abort(); | |
| }; | |
| } | |
| // Wrap other Promise instances to AbortablePromise | |
| static from = <T>(promise: Promise<T>): AbortablePromise<T> => { | |
| // If promise is already an AbortablePromise, return it directly | |
| if (promise instanceof AbortablePromise) { | |
| return promise; | |
| } | |
| return new AbortablePromise<T>((resolve, reject) => { | |
| promise.then(resolve).catch(reject); | |
| }); | |
| }; | |
| } |
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