Unable to get hidden form value into javascript variable

Question

I have a form with several fields. The value of one of the hidden fields is passed in the URL along with some other input values like this:

example.html#firstname=Homer&lastname=Simpson&itype=TARGET

I have a javascript that parses the URL and that is populating the form just fine. The output of the form contains all of the values passed from the url, so I know the variable are getting passed to the form fields.

My issue is - I want to be able to setup an if statement to change the text of one of the headings based on the value of itype.

Here's my code:

        var itypestuff = document.getElementById("itype").value;

        document.write ("<p>The value of the variable is " + itypestuff.value + "</p>");

        if( itypestuff == "TARGET" ){
           document.write("This is the target");
        }

        else{
           document.write("This is not the target");
        }

I added the first document.write statement as a debug and it's coming back with: The value of the variable is undefined

Here's what the itype field variable looks like:

    <input type="hidden" name="itype" id="itype" value="">

Any ideas how I can get the variable from the URL into my javascript variable so I can do my if statement?

Try var itypestuff = document.getElementById("itype"); (yes, without the value there) — Ismael Miguel
– Ismael Miguel, Commented Jul 30, 2015 at 14:09
Why do you need to read the value from a hidden field if you are already touching the value in code when you strip it out of the url? Place it in a variable at that moment and then use it later in your processing of the page. This way you would totally skip messing with the DOM. — Chris
– Chris, Commented Jul 30, 2015 at 14:13
My code for stripping it out of the URL and assigning it to form variables is just a loop so it doesn't look at particular variables - it just separates them all and overwrites the empty values for the visible and hidden fields. — homermac
– homermac, Commented Jul 30, 2015 at 14:26

6be709c0 · Accepted Answer · 2015-07-30 14:31:18Z

2

Change :

 document.write ("<p>The value of the variable is " + itypestuff.value + "</p>");

To

document.write ("<p>The value of the variable is " + itypestuff + "</p>");

OR

Change

var itypestuff = document.getElementById("itype").value;

To

var itypestuff = document.getElementById("itype");
// And 
if( itypestuff.value == "TARGET" ){ //...

EDIT

You have to change your html like that :

<input type="hidden" name="itype" id="itype" value="<?= htmlspecialchars($_GET['itype']); ?>">

And call : example.php?firstname=Homer&lastname=Simpson&itype=TARGET

edited Jul 30, 2015 at 14:31

answered Jul 30, 2015 at 14:10

6be709c0

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8 Comments

homermac Over a year ago

When I make either of those changes - the document.write statement comes back with a blank (ie The value of the variable is (nothing here))

6be709c0 Over a year ago

Becauce value="" is null. Change by : value="TARGET" in your HTML.

homermac Over a year ago

The problem is - I want to pass the value of that form variable from the URL - so it will be TARGET sometimes - but will be MISSEDTARGET other times - I want it to be dynamic and not fixed. LIke I said - the output when I submit the form of itype is showing TARGET - but it's like it's not getting set in the timeline when the javascript is interrogating the form value.

6be709c0 Over a year ago

Look my edits. I've added what you missing in your html.

homermac Over a year ago

When I do the PHP code - I get: The value of the variable is [object HTMLInputElement]

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