Solved

Variable with global scope not recognized inside function

Posted on 2014-11-05
6
267 Views
Last Modified: 2014-11-06
The script below works fine. Clicking on the button immediately grays it out.

<html>
<head></head>
<script>
 
function disableButton() {      
   document.getElementById("button1").disabled = true;          
}

</script>

<body>

<input type="button" value="click here" id="button1" onclick = "disableButton()"/>
 
</body>
</html>

But when I create reference to the button with global scope, the script no longer works. Clicking the button no longer disables it. The modified script below does not work.

<html>
<head></head>
<script>
 
myButton = document.getElementById("button1");

function disableButton() {      
  myButton.disabled = true;          
}

</script>

<body>

<input type="button" value="click here" id="button1" onclick = "disableButton()"/>
 
</body>
</html>


Shouldn't myButton be recognized inside the function?
0
Comment
Question by:MBarongan
  • 3
  • 2
6 Comments
 
LVL 142

Accepted Solution

by:
Guy Hengel [angelIII / a3] earned 500 total points
ID: 40425578
this is because the script is run before the body is actually loaded
you have to move the script below the body part, then it shall work
0
 

Author Closing Comment

by:MBarongan
ID: 40425587
It worked! Thank you. I knew it was something simple I wasn't doing.
0
 

Author Comment

by:MBarongan
ID: 40425604
I moved to script to an external js file and now it doesn't work again. Is there something I need to put in the external file to make it work?  All I have is this:

var myButton = document.getElementById("button1");

function disableButton() {      
  myButton.disabled = true;  
       
}
0
DevOps Toolchain Recommendations

Read this Gartner Research Note and discover how your IT organization can automate and optimize DevOps processes using a toolchain architecture.

 
LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 40425637
I presume that again, the script file is referenced in the header part ...

what you may do, in any case, is something like this:

var myButton = null;

function setmyobjects() {
 if ( myButton = null ) {
     myButton document.getElementById("button1");
    }
 }

function disableButton() {     
  setmyobjects(); 
  myButton.disabled = true;  
       
} 

Open in new window


so, your function setmyobjects sets all the objects you would need, testing however only one (which should be enough)
all your functions that needs such "global" objects first call this function
0
 

Author Comment

by:MBarongan
ID: 40425672
Got it working now. Thanks again.
0
 
LVL 52

Expert Comment

by:Julian Hansen
ID: 40425704
You probably want to look at the onload function as well. This is called when the document is ready. By using onload you can place your script anywhere (although at the bottom is usually a good place - but not always feasible)
<html>
<head></head>
<script type="text/javascript">

var myButton; // Declare the variable

// Wait for the DOM to be ready
window.onload = function() {

  // Set your button  
  myButton = document.getElementById("button1");
}

// myButton is now pointing to the <input>
function disableButton() {      

  myButton.disabled = true;          

}
</script>
<body>
<input type="button" value="click here" id="button1" onclick = "disableButton()"/>
</body>
</html>

Open in new window

0

Featured Post

3 Use Cases for Connected Systems

Our Dev teams are like yours. They’re continually cranking out code for new features/bugs fixes, testing, deploying, testing some more, responding to production monitoring events and more. It’s complex. So, we thought you’d like to see what’s working for us.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Windows Script Host (WSH) has been part of Windows since Windows NT4. Windows Script Host provides architecture for building dynamic scripts that consist of a core object model, scripting hosts, and scripting engines. The key components of Window…
When we want to run, execute or repeat a statement multiple times, a loop is necessary. This article covers the two types of loops in Python: the while loop and the for loop.
Viewers will learn how to properly install Eclipse with the necessary JDK, and will take a look at an introductory Java program. Download Eclipse installation zip file: Extract files from zip file: Download and install JDK 8: Open Eclipse and …
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

895 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now