External JavaScript File

noobdesigner · May 20, 2020

Hello,

first of all, sorry for the extremly nooby quastion and my not so good English, but this makes me insane.

My HTML Code --> index.html:

<html>
<head>
    <script src="main.js"></script>
</head>
<body>
    <input id="btn" type="button" value="Button">
</body>
</html>

And my JavaScript Code --> main.js:

function test()
{
    alert("Test");
}
btn.addEventListener ("click", test);

It is written everywhere, that the <script src="xyz"></script> should be written as high as possible, respectivly within the <head> Tags.
But the code above do not work --> Why??

The code works only if my script is written/loaded after the <input> Tag. Is this works as desinged? Should the script import really written at the end of the HTML page?

Thanks in advance.

Edited May 20, 2020 by noobdesigner

Ingolme · May 20, 2020

The page loads in order from top to bottom and the Javascript runs as soon as it can even if the rest of the page has not loaded yet.

One way to solve it is to always put scripts before the closing </body> tag.

Another way is to have the code wait for the page to load before assigning the event listener. This can be done with the DOMContentLoaded event:

window.addEventListener("DOMContentLoaded", attachEvents);

function attachEvents() {
  var p = document.getElementById("btn");
  p.addEventListener ("click", test);
}

function test() {
  alert("Test");
}

noobdesigner · May 20, 2020

Ok, thank you very much. So that is how its works.The Book i am working on, did not say anything about it...

Sign In

External JavaScript File

Recommended Posts

noobdesigner

Link to comment

Share on other sites

Ingolme

Link to comment

Share on other sites

noobdesigner

Link to comment

Share on other sites

Create an account or sign in to comment

Create an account

Sign in

Browse

Activity