Waiting for dynamically loaded script

Question

In my page body, I need to insert this code as the result of an AJAX call:

    <p>Loading jQuery</p>
    <script type='text/javascript' src='scripts/jquery/core/jquery-1.4.4.js'></script>
    <p>Using jQuery</p>
    <script type='text/javascript'>
        $.ajax({
            ...
        });
    </script>

I can't use $.load() since the document has already loaded, so the event doesn't fire.

Is this safe? If not, how do I make sure the jquery script has loaded before my custom, generated code is executed.

Answer 1

It is pretty safe. Historically, <script> tags are full blocking, hence the second <script> tag can't get encountered befored the former has finished parsing/excuting. Only problem might be that "modern" browsers tend to load scripts asynchronously and deferred. So to make sure order is correct, use it like this:

<p>Loading jQuery</p>
<script type='text/javascript' async=false defer=false src='scripts/jquery/core/jquery-1.4.4.js'></script>
<p>Using jQuery</p>
<script type='text/javascript'>
    $.ajax({
        ...
    });
</script>

However, it's probably a better idea it use dynamic script tag insertion instead of pushing this as HTML string into the DOM. Would be the same story

var scr  = document.createElement('script'),
    head = document.head || document.getElementsByTagName('head')[0];
    scr.src = 'scripts/jquery/core/jquery-1.4.4.js';
    scr.async = false; // optionally

head.insertBefore(scr, head.firstChild);