How to get a javascript alert?

Question 1

Your script tag to pull in jQuery is using the (Common|General) Internet Syntax Scheme. This tells the browser to use whatever scheme was used to load the page in loading the script. It is helpful for sites which respond to both http and https.

If you are viewing your file locally using the file:// scheme, then you should see an error that $ is not defined. This is because the script does not live at:

file://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js

Please use this src in the script tag when loading locally:

<script src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>

Question 2

Path to src should be complete if you have hosted it somewhere.You have not added correct path to jquery library. Everything will work accordingly once you do that.

<script src="http://code.jquery.com/jquery-latest.js"></script>

Demo

Question 3

According to your url starting with // the browser tries to load that file from your local file system if you're locally testing your site using an url like file://. In that case you're not loading jQuery, so the $ is undefined and your code never executed.

Use the script tag like that for local tests:

<script src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>

If you run your site on a web server, the cdn-style starting with // will work again.

Question 4

Code looks fine

I think you are testing in IE < 9 (jQuery 2.x not supporting IE 8)

Please change the browser or load jQuery version like 1.9 and test it

Question 5

You have to update query script src to 'http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js'

I recommend to download the jQuery script then add it to your project locally instead of the remote one

Question 6

use <script type="text/javascript" src="http://code.jquery.com/jquery-1.10.1.min.js"> and practise to insert html tag

HTML:

<!doctype html>
<html>
    <head>
        <script type="text/javascript" src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
        <script type="text/javascript">
            $(document).ready(function(){
                $("#sendButton").click(function(){
                    alert("clicked!!");
                });
            });
        </script>
    </head>
    <body>

    <form id="send-message-area">
        <input type="button" id="sendButton" value="Send Message">
    </form>
</body>
</html>

Question 7

You are missing to include http:/ in your script src.

Either change your script tag like this:

 <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>

or download the Jquery file and refer locally.

Question 8

Change your path to

<script src="http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>

and try to use jquery 1.10 for less than ie9 browser

<!--[if lt IE 9]><script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script><![endif]-->
<!--[if IE 9]><!--><script src="http://ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script><!--<![endif]-->