Question

I have a function which showing progress of uploading files to the server:

function progress(event) {
...
}
...
for (var i = 0; i<files.length; i++) {
    xhr.upload.onprogress = progress;
}

progress function is in for loop, and executes once for every file.
In progress function I want to write how many percent is uploaded, I can do it for one file, but if I uploading not one file, then I don’t know how to make progress for every file.
Can I add a parameter of loop to progress function?

Answer 1

You can use an anonymous function to give progress function additional parameter:

function progress(event, file) {
   ...
}

for (var i = 0; i<files.length; i++) {
    xhr.upload.onprogress = function(event) {
        progress(event, files[i]);
    }
}

But this code will not work because progress will take the last file item every time. To avoid it you must use a closure:

function progress(event, file) {
    ...
}

for (var i = 0; i<files.length; i++) {
    (function(xhr, file) {
        xhr.upload.onprogress = function(event) {
            progress(event, file);
        }
    })(xhr, files[i]);
}

P. S. Sorry, my first anwser was wrong, I’ve deleted it.