I've been working in asp.net webforms and I've been making a UserControl that depends on a small bit of javascript which is in an external file.
I want to be able to put a reference to the javascript inside the UserControl to ensure that it gets loaded on the page, but the problem is that the UserControl can appear multiple times on a page so I only want the script to be loaded with the first instance of the UserControl.
Is there an easy way to do this in ASP.NET Webforms?
Use the ClientScriptManager's RegisterClientScript() methods to handle this. In your case, since you're including the script from an external file, use RegisterClientScriptInclude().
Alternately, if you're using UpdatePanels, use ScriptManager's equivalent Register...() methods.
Reference the script in the HEAD of the page itself.
<html>
<head>
...
<script src="<name of file>" type="text/javascript"></script>
...
</head>
<body>
...
</body>
</html>
You could also handle this issue in the JS file itself, if you control its content.
var myObj = myObj || {}; // Variable to namespace your work
// Make sure we do our work only once
if (!(myObj.token)) {
// do our work here...
myObj.token = {}; // this ensure we won't enter the if block the next time
}