Change html dir attribute using jQuery

I want to change HTML dir attribute once the page loads; how can I do that? Do I need to use the .ready() function? Currently it looks like:

jQuery("html[lang=ar]").attr("dir", "rtl")
            .find("body").addClass("right-to-left");

How can I write it in a script; do i need to write in .ready() function or .load()?

<div class="header">
<script src="http://code.jquery.com/jquery-latest.js"></script>
<script>
jQuery("html").attr("dir", "rtl")?
</script>

The code appears like this:

This is my CSS

body.right-to-left li {
    float:right;
    direction: rtl;
}

Solution

simple as it can be...

put your code inside...document.ready()

<script>
$(document).ready(function(){
     $("html[lang=ar]").attr("dir", "rtl")
        .find("body").addClass("right-to-left");
});
</script>

and a link that explain about ready() and load() function..