从循环中一次发送一个AJAX请求 [英] Sending one AJAX request at a time from a loop

问题描述

我知道这个问题已被无数次询问，但我无法弄清楚我的生活如何让这个答案在我的案例中起作用：等待异步javascript函数返回

I know this question has been asked countless times, but I cant figure out for the life of me how to make this answer work in my case: wait for async javascript function to return

我正在循环播放一些电视频道 在外环中，然后循环遍历内环中的一周中的日期。在内部循环中，我向服务器发出ajax请求以获取数据，然后我将其存储/缓存以供以后使用，如此

I'm looping through some "tv channels" in the outerloop and then looping through dates in the week in the innerloop. In the inner loop I make a ajax request to a server to fetch the data and I then store/cache it for later use like so

var dates = []; //<-- Contains a list of dates for the coming week 
var baseUrl = "http://www.someserver.com";
var storedChannels = [1,2,3,4,5,6,7,8,9,10,45,23,56,34,23,67,23,567,234,67,345,465,67,34];

for(ch = 0; ch < storedChannels.length; ch++) {   
    var channel = storedChannels[ch];
    for(d=0; d < 7; d++) {
        var currentDate = dates[d];
        ajax({    
            url: baseUrl+"?ch="+channel+"&dt=currentDate"+,
            complete: function(res) {
                CMLocalStore.setString('ch' + ch + "_" + scheduleDay, res);
            },
        });
        //Want to wait here till the ajax request completes.
        //Do not want to continue to next iteration.
        //Do not want to fire of 50 bazillion ajax requests all at once
        //Why? Very limited bandwidth scenario, plenty of channels  
    }
}

PS：没有请JQuery！简单的JS解决方案

PS: NO JQuery please! Plain JS solutions only

非常感谢！

推荐答案

你想要的东西像这样。我没有测试过，但希望你能得到这个想法。

You want something like this. I haven't tested it, but hopefully you should get the idea.

var dates = []; //<-- Contains a list of dates for the coming week 
var baseUrl = "http://www.someserver.com";
var storedChannels = [1,2,3,4,5,6,7,8,9,10,45,23,56,34,23,67,23,567,234,67,345,465,67,34];

function ProcessNext(ch, d) {
    if (d < 7) {
        d++;
    } else {
        d=0;
        if (ch < storedChannels.length) {
            ch++;
        } else {
            return;
        }
    }

    var channel = storedChannels[ch];
    var currentDate = dates[d];
    ajax({    
        url: baseUrl+"?ch="+channel+"&dt=currentDate"+,
        complete: function(res) {
            CMLocalStore.setString('ch' + ch + "_" + scheduleDay, res);
            ProcessNext(ch, d);
            },
    });
}

ProcessNext(0, 0);

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