How to insert element as a first child?

Extending on what @vabhatia said, this is what you want in native JavaScript (without JQuery).

ParentNode.insertBefore(<your element>, ParentNode.firstChild);


Try the $.prepend() function.

Usage

$("#parent-div").prepend("<div class='child-div'>some text</div>");

Demo

var i = 0;
$(document).ready(function () {
    $('.add').on('click', function (event) {
        var html = "<div class='child-div'>some text " + i++ + "</div>";
        $("#parent-div").prepend(html);
    });
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<div id="parent-div">
    <div>Hello World</div>
</div>
<input type="button" value="add" class="add" />