If you are using Razor view engine then edit the _Layout.cshtml file. Move the @Scripts.Render("~/bundles/jquery") present in footer to the header section and write the javascript / jquery code as you want:
@Scripts.Render("~/bundles/jquery")
<script type="text/javascript">
$(document).ready(function () {
var divLength = $('div').length;
alert(divLength);
});
</script>