JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
<li class="dropped" data-order="0" data-id="1" data-content="blabla">first</li>
<li class="dropped" data-order="0" data-id="2" data-content="another content">second</li>
</ul>

<div id="result"></div>

<button class="send">Send</button>

JavaScript

$(".send").click(function() {

    var itterate = $(".dropped");
    var data_array = new Array();

    for (var i in itterate.data()) {

        var sub_array = new Array();
        sub_array['data-order'] = i;
        sub_array['data-id'] = itterate.data()[i];
        sub_array['data-content'] = itterate.data([i]);

        data_array.push(sub_array);

    }

    var serialized = $.param(itterate.serializeArray().concat(data_array));

    $("#result").text(serialized);

});