Javascript, jQuery multiple AJAX requests at same time

Question

function makeCall(file, handlerFile, sendMethod, formData) {
    //console.log(instance.files);

    $.ajax({
        url: handlerFile,
        type: sendMethod,
        xhr: function() {  // Custom XMLHttpRequest
            var xhr = $.ajaxSettings.xhr();

            if(xhr.upload) { // Check if upload property exists
                xhr.upload.addEventListener('progress', progressHandlingFunction.bind(file)); // For handling the progress of the upload
                //xhr.upload.addEventListener('loadend', successHandler.bind(xhr));
            }

            //console.log(xhr);

            return xhr;
        },
        beforeSend: beforeSendHandler.bind(file),
        success: completeHandler.bind(file),
        //error: errorHandler,
        data: formData, // Form data
        dataType: 'json',
        cache: true,
        //async: false,
        contentType: false,
        processData: false
    });

}



$(".afu-input").on('change', function() {
        var i = 0;
        var length = this.files.length;
        var files = this.files;

        var calling = setInterval(function() {
            var file = files[i];
            console.log(file);

            uid  = generateUniqueId();
            file.id = uid;

            var formData = null;
            formData = new FormData();

            formData.append(i, file);
            formData.append(i, [uid]);

            makeCall(file, handlerFile, sendMethod, formData);

            i++;

            if (i >= length) {
                clearInterval(calling);
            }
        }, 2000); // Delay is for testing. Normaly there is no delay
}

I'm trying to upload file one by one. But the problem is that ajax sending request properly, but getting only one(first) data return.

My goal is to create script which uploads images(and later other files) on input[type=file] change. I tried to upload multiple files with one request, but progress event registering them as one. I had idea to slice(chunk) files into pieces ant send them, but this variant seems easier(just need to make it work, then I improve it). Thanks.

Answer 1

It's easy to make it with jQuery.when();

Ajax calls can be any number. So you need to use it with apply(); and create array of ajax calls. Now code looks like this:

function makeCall(file, formData) {
    return $.ajax({ // It's necessary to return ajax call 
       url: 'handler.php',
       type: 'POST',
       xhr: function() { // Creating custom XHR to register progress event(If you know better solution - please post ir)
           var xhr = $.ajaxSettings.xhr();

           if (xhr.upload) { // Check if upload property exists
               xhr.upload.addEventListener('progress', progressHandlingFunction.bind(file)); // Registering progress event
           }

           return xhr;
       },
       // Events handlers
       beforeSend: beforeSendHandler.bind(file),
       success: completeHandler,
       data: formData,
       dataType: 'json',
       cache: true,
       contentType: false,
       proccessData: false
    });
}

$('.afu-input').on('change', function() {
    var files = this.files;
    var calls = [];

    $.each(files, function(i, file) {
        uid = generateUniqueId();
        file.id = uid;

        var formData = new formData();

        formData.append(0, file); // Just easier to set index to 0 cause for every file returning new obejct, so is no point to set more indexes

        calls.push(makeCall(file, formData)); // And finally pushing calls to array
    });

    // Using jQuery.when
    // Cause I don't know how many calls will be I'm using "apply" so I can add array instead of one by one calls
    $.when.apply($, calls); // Exactly I don't know why need "$"
}

function beforeSendHandler() {
    console.log(this);
}

function completeHandler(data) {
    console.log(data);
}

function progressHandlingFunction(e) {
    console.log(e);
    console.log(this);
}