Abortable Promise

abortable-promise.ts

export class AbortablePromise<T> extends Promise<T> {
    #aborted = false;

    abort() {
        this.#aborted = true;
    }

    then<TResult1 = T, TResult2 = never>(
        onfulfilled?:
            | ((value: T) => TResult1 | PromiseLike<TResult1>)
            | null
            | undefined,
        onrejected?:
            | ((reason: any) => TResult2 | PromiseLike<TResult2>)
            | null
            | undefined
    ): Promise<TResult1 | TResult2> {
        return super.then(
            (value) => {
                if (this.#aborted) {
                    // create new promises each time so that everything can be GC'd correctly
                    return new Promise<TResult1>(() => {
                        /* never fulfill */
                    });
                } else if (onfulfilled) {
                    return onfulfilled(value);
                } else {
                    return value as any;
                }
            },
            (reason) => {
                if (this.#aborted) {
                    // create new promises each time so that everything can be GC'd correctly
                    return new Promise<TResult2>(() => {
                        /* never fulfill */
                    });
                } else if (onrejected) {
                    return onrejected(reason);
                } else {
                    throw reason;
                }
            }
        );
    }

    // `catch` and `finally` both internally call `then`, so only `then` needs to be overridden
}