Nov '18

POSTing Files with AJAX The Easy Way

Ok many of you may already know this one, but it’s a relatively new one to me, and since non-HTML5 browsers are now mostly gone the way of the dinosaur, I’m much more comfortable relying on its elements for my core functionality. If you are still on IE9 or below then you deserve all you get!

This is as simple as I can make an AJAX form submission handler, that will also deal with files. It uses the HTML5 FormData object to serialise all the form data, including files, and allow us to pass it with the AJAX POST request.

$('.my-form').on('submit', function(e) {

    var form_data = new FormData($(this)[0]);

        type: 'POST',
        url: $(this).attr('action'),
        data: form_data,
        dataType: 'json',
        cache: false,
        contentType: false,
        processData: false,
        success: function(response) {
            // Wahey!
        error: function() {
            // Oh dear

    return false;

The ‘cache’, ‘contentType’ and ‘processData’ flags ARE necessary to make this work properly. The ‘dataType’ is optional, but if your server doesn’t send back JSON in response to an AJAX request as standard then you need to have a word with yourself!

Also notice that the FormData object needs the DOM version of the form, not the jQuery object, hence the need for “$(this)[0]” in the constructor.

Job. Done.

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