Tips for preventing premature ajax data requests in a for loop before the previous one has finished

Question

Tips for preventing premature ajax data requests in a for loop before the previous one has finished

Looking to make multiple ajax requests and return the data one by one in a for loop. However, sometimes new data is sent before the previous request is completed, resulting in incorrect data being returned. This doesn't happen often, but I need help solving this issue.

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

I've tried using setTimeout in the loop, but the results were incorrect.

I prefer using pure javascript, no JQuery or other library. I came across "complete:" and ".done()" in JQuery, but I'm not sure if they're what I need. Can someone guide me on how to solve this problem with raw javascript?

javascript ajax loops delay

Answer 1

Answer №1

When tackling this issue, my go-to approach is usually using recursion. However, I am unsure if there are any potential downsides to this method. The code snippet that I typically use looks something like the following:

function handleRequest(currentIndex, list){
    $.ajax({
        url: list[currentIndex],
        ....
        complete: function(){
            //perform actions here
            if (currentIndex + 1 < list.length) handleRequest(currentIndex + 1, list);
        }
    });
}

handleRequest(0, arrayToProcess);

Answer 2

When tackling this issue, my go-to approach is usually using recursion. However, I am unsure if there are any potential downsides to this method. The code snippet that I typically use looks something like the following:

function handleRequest(currentIndex, list){
    $.ajax({
        url: list[currentIndex],
        ....
        complete: function(){
            //perform actions here
            if (currentIndex + 1 < list.length) handleRequest(currentIndex + 1, list);
        }
    });
}

handleRequest(0, arrayToProcess);

Answer 3

Answer №2

To overcome the challenge of completing one ajax call and waiting for another request until the first one is finished, a recursive call was utilized to work its magic.

var queue_element = ["a","b","c","d","e","f","g"];

var execute_queue = function(i){    
 $.ajax( {    
    url: queue_element[i],
    success: function(
    {
        i++;    // moving on to the next queue entry

        // checking if next entry exists
        if (queue_element[i] != undefined)
        {
            execute_queue(i);
        }
    }

  }); // end of $.ajax( {...

}; // end of execute_queue() {...

var index = 0;

execute_queue(index); // let's go!

Answer 4

To overcome the challenge of completing one ajax call and waiting for another request until the first one is finished, a recursive call was utilized to work its magic.

var queue_element = ["a","b","c","d","e","f","g"];

var execute_queue = function(i){    
 $.ajax( {    
    url: queue_element[i],
    success: function(
    {
        i++;    // moving on to the next queue entry

        // checking if next entry exists
        if (queue_element[i] != undefined)
        {
            execute_queue(i);
        }
    }

  }); // end of $.ajax( {...

}; // end of execute_queue() {...

var index = 0;

execute_queue(index); // let's go!

Tips for preventing premature ajax data requests in a for loop before the previous one has finished

Answer №1

Answer №2

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