Q:

External scripts not working in Windows Phone App 8.1

I've added a WebView into my project. If I navigate to the html file that contains external javascript files they don't work. Bit if I write the javascript code hardcoded into the html file it works properly. 
Here is the html portion:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
    <title></title>
    <script type="text/javascript" src="testjs.js"></script>
</head>
<body>
    <div id="abcd"></div>
    <br/>
    hello! this is a simple html block. 
</body>
</html>

Here is the javascript portion:
document.getElementById("abcd").innerHTML = "New text!";

When I open the webview it shows 
hello! this is a simple html block., 
but if the javascript code worked it would show 
New Test!
hello! this is a simple html block.
Here is the folder structure:

A:

src="testjs.js" is correct. The issue is not related to the path. 
[Update 1]
Your code should work as we usually do for web development. But seems we need to make sure the html element used in the script has been initialized, so we have to put the  to the end of the body element. Please try the following html code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
    <title></title>
    
</head>
<body>
    <div id="abcd">a</div>
    <br />
    hello! this is a simple html block.

    <script type="text/javascript" src="testjs.js"></script>
</body>
</html>

[Update 2]
Also check if you have changed the build action for testjs.js to content. go to Solution Explorer -> right click on testjs.js -> Properties -> change Build Action to Content. That will make sure the .js file will be deployed as part of you app.

