jQuery Deferreds的异步循环（承诺） [英] Asynchronous Loop of jQuery Deferreds (promises)

问题描述

我正在努力创造我认为被称为瀑布的东西。我想顺序处理一系列异步函数（jQuery promises）。

I am trying to create what I think is referred to as a "Waterfall". I want to sequentially process an array of async functions (jQuery promises).

这是一个人为的例子：

function doTask(taskNum){
    var dfd = $.Deferred(), 
        time = Math.floor(Math.random()*3000);

    setTimeout(function(){
        console.log(taskNum);
        dfd.resolve();
    },time)

    return dfd.promise();
}

var tasks = [1,2,3];

for (var i = 0; i < tasks.length; i++){
    doTask(tasks[i]);
}

console.log("all done");

我希望它按照执行顺序完成任务（存在于数组中）。因此，在这个例子中，我希望它执行任务1并等待它解决然后执行任务2等待它解决，执行任务3等并且日志全部完成。

I would like it to complete the task in the order they are executed (present in the array). So, in this example I want it to do task 1 and wait for it to resolve then do task 2 wait for it to resolve, do task 3 etc and the log "all done".

也许这很明显，但我一直试图在整个下午解决这个问题。

Maybe this is really obvious but I've been trying to figure this out all afternoon.

推荐答案

我尝试使用 $（）。队列而不是 $。延期这里。将函数添加到队列中，并在准备好时仅调用下一个函数。

I'd try using $().queue instead of $.Deferred here. Add the functions to a queue, and only call the next one when ready.

function doTask(taskNum, next){
    var time = Math.floor(Math.random()*3000);

    setTimeout(function(){
        console.log(taskNum);
        next();
    },time)
}

function createTask(taskNum){
    return function(next){
        doTask(taskNum, next);
    }
}

var tasks = [1,2,3];

for (var i = 0; i < tasks.length; i++){
    $(document).queue('tasks', createTask(tasks[i]));
}

$(document).queue('tasks', function(){
    console.log("all done");
});

$(document).dequeue('tasks');

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