Why isn't this working

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drater1000

I don't understand why paragraph(demo) is not changing into "IT WORKS!!!"
Here is the script:

function submitinfo()

{
var firstname = document.getElementById("firstname").value;
var lastname = document.getElementById("lastname").value;
var middlename = document.getElementById("middlename").value;

alert("Hello " + firstname + " " + middlename + " " + lastname);

if (middlename == null);
{
getElementById("demo").innerHTML= "IT WORKS!!!";
}

}

</script>
First Name: ....<input type="text" id="firstname">
<br />
Middle Name: <input type="text" id="middlename">
<br />
Last Name: ....<input type="text" id="lastname">
<br />
<input type="button" value="Submit" onclick="submitinfo()">
<br />
<br />
<p id= "demo"></p>
</body>
</html>

Lucas1

Try a

<span id="demo"> <span>

I have an exact example of what you want give me a second to find it.#

Also I wouldn't write the javascript in the same file as the HTML. It's a bad habit.

Put this in your HTML Header.

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

And simply open a new notepad++ and save a blank document as javascript.js and put all your js code in there.

xelawho

try it with

document.getElementById("demo").innerHTML= "IT WORKS!!!";

xelawho

Lucas1;1228413 wrote:
Also I wouldn't write the javascript in the same file as the HTML. It's a bad habit.

actually it's a very good habit when posting questions here to include all the relevant information (rendered html, js and css) in the one code block. It saves people having to ask to see other bits and makes it easier to test your code. Once you have your code working you can do what you like with it.

I've never been hugely swayed by the separation of concerns arguments. If you are working on large frameworks with multiple pages depending on the same external files, of course it makes sense. But to create a separate js file for a few lines of code seems unnecessarily dogmatic.

What is important is not to put javascript in the head, either as an external file or a code block. It will slow down the loading of the page (as the script has to be read before the html is rendered) and make it necessary for any script accessing html elements on page load to be wrapped in a window onload function. The best place for javascript - either inline or as an external file reference - is just before the closing </body> tag

Troy_III

What do you mean by :

if (middlename == null);

why null and what did you expect from that?!

try to keep it simple and do

if (!middlename);

and you're on gear.

xelawho

not with
getElementById("demo").innerHTML

that will never work...

Troy_III

seeing this: getElementById("demo").innerHTML= "IT WORKS!!!";}}</script>
First Name: ....<input type="text" id="firstname">...

I presumed he was shorting out the illustration of his problem and that on his original code stands a properly written document.getElementBy(id) instead.

Troy_III

....

Logic_Ali

My answer to this would have been 'Use the error console", but I don't like to repeat myself too often.

Troy_III

and how would that help against syntactically correct code but semantically wrong meaning of a chosen expression? nothing can guard you against your own laspus lingua.

Logic_Ali

Troy III;1228457 wrote:
and how would that help against syntactically correct code but semantically wrong meaning of a chosen expression?

It wouldn't; It wasn't.