I want the current tab url to be display in the pop up after clicking the extension. I have a popup html and popup.js. For testing purpose, I been trying to alert the tab url instead of replacing the html element.
Manifest.json
{
    "manifest_version": 2,
    "name": "first extension",
    "version": "1.0",
    "browser_action": {
        "default_icon": "icon.png",
        "default_popup": "popup.html",
        "default_title": "Share it!"
    },
    "permissions": [
        "activeTab"
    ]
}
popup.html
<!DOCTYPE html>
<html>
<head>
    <script type="text/javascript" src="popup.js"></script>
    <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
    URL:
    <p>www.blahblah.com</p>
    <form>
        Title:<br />
        <input type="text" name="title"><br />
        Description:<br />
        <textarea rows="4"></textarea><br />
        <button>Get</button>
    </form>
</body>
</html>
popup.js
chrome.tabs.getCurrent(function(tab){
        alert(tab.url);
    }
);
 
    