generator practical-use-cases

[vaakian]

TODO：细品理解以下代码

function httpFiFoRequestsExecutor({
    onTaskSuccess,
    onTaskFail,
}) {
    async function* execute(taskInfos, props) {
        const {
            taskIdentifier,
            taskFn
        } = taskInfos || {};
        try {
            const result = await taskFn(props);
            if (onTaskSuccess) {
                onTaskSuccess(
                    taskIdentifier,
                    result[result.length - 1],
                    result
                );
            }
            const nextTask = yield result; // waiting for the next task
            yield* execute(nextTask, result); // restart from the begin : recursive call
        } catch (reason) {
            if (onTaskFail) {
                onTaskFail(taskIdentifier, reason);
            }
            const nextTask = yield reason; // waiting for the next task
            yield* execute(nextTask, props); // restart from the begin : recursive call
        }
    }

    // Initiate the async generator
    // and move the cursor to the first yield.
    const iterator = execute({
        taskIdentifier: null,
        taskFn: () => [],
    }, []);
    iterator.next();

    // next返回上次任务的结果，而参数将新的任务放进去。
    const executeTask = (taskIdentifier, taskFn) => iterator.next({
        taskIdentifier,
        taskFn,
    });

    return {
        executeTask,
        cancel: () => iterator.return()
    };
}

const httpRequestsExecutor = httpFiFoRequestsExecutor({
    onTaskSuccess: (requestId, requestResponse, responsesStack) => {
        console.log('onTaskSuccess requestId : ', requestId);
        console.log('onTaskSuccess requestResponse : ', requestResponse);
        console.log('onTaskSuccess responsesStack : ', responsesStack);
    },
    onTaskFail: (requestId, requestError) => {
        console.log('onTaskFail requestId : ', requestId);
        console.log('onTaskFail requestError : ', requestError.message);
    },
});

httpRequestsExecutor.executeTask('1', celebrities => Promise.resolve([...celebrities, 'Albert Einsten']));

httpRequestsExecutor.executeTask('2', celebrities => Promise.resolve([...celebrities, 'Nicolas Tesla']));

// asyncHttpFifoExecutor.cancel();

httpRequestsExecutor.executeTask('3', null);

httpRequestsExecutor.executeTask('4', celebrities => Promise.resolve([...celebrities, 'Marie Curie']));