Passing a variable to a function

[ideasworking]

Hello,

I could use a little help with a function. I wrote a function that should update the value in a text box named "CityUsage" depending on the state of a checkbox However the code just isn't working. Can someone help me identify the problem?

Here's my function...

<script language="JavaScript">
function cc(a)
{
var PreviousValue = 771970    
if (a=1)
{document.forms["WaterReadings"].CityUsage.value= document.forms["WaterReadings"].NewCityWaterReading.value - PreviousValue}
else
{document.forms["WaterReadings"].CityUsage.value= document.forms["WaterReadings"].NewCityWaterReading.value - PreviousValue + 1000000}
}

I call the function from the keyup event of a text box as shown below. I put 1 in the call to the function for testing purposes.

<input name="NewCityWaterReading" type="text" id="NewCityWaterReading" onKeyUp="cc(1)" value="771970" maxlength="10" align="right">

I think the actual call to the function should be something like this... but maybe not???

<input name="NewCityWaterReading" type="text" id="NewCityWaterReading" onKeyUp="cc(<?PHP echo "document.forms["WaterReadings"].Checkbox.value" ?>)" value="771970" maxlength="10" align="right">

 

[BillyRayPreachersSon]

You need 2 equals signs to test for equality:

if (a=[!]=[/!]1)

Hope this helps,
Dan



Coedit Limited - Delivering standards compliant, accessible web solutions

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[/tt]

 

[BillyRayPreachersSon]

In fact, I'd modify the script to be a bit neater, and add in some semicolon delimiters (not always needed, but should be present, really):

<script type="text/javascript">
function cc(a) {
	var PreviousValue = 771970;
	var frm = document.forms['WaterReadings'].elements;
	if (a == 1) {
		frm['CityUsage'].value = frm['NewCityWaterReading'].value - PreviousValue;
	} else {
		frm['CityUsage'].value = frm['NewCityWaterReading'].value - PreviousValue + 1000000;
	}
}
</script>

Dan



Coedit Limited - Delivering standards compliant, accessible web solutions

[tt]Dan's Page [blue]@[/blue] Code Couch

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[/tt]

 

[ideasworking]

Thanks for the response. I tried your recommendations and made some changes; still it didn't work. The biggest problem seems to be passing the value of the the checkbox to the function. With the code I have below no alert is raised. If I change the code so that var a = '1' then the alert is raised. Any suggestions?

Thanks,
Lou

<script language="JavaScript">

function ccw()
{
var a = document.forms['WaterReadings'].['CityWaterRollOver'].value; 
if(a == '1'){
alert ('Hello');
} else {
alert ('Goodbye');
}
}
</script

 

[BillyRayPreachersSon]

Where did you get this crazy syntax from?

document.forms['WaterReadings'].['CityWaterRollOver'].value;

It's not legal, and will probably be causing your code to error. Try putting in the syntax I gave you - which works.

You're also missing a closing ">" off of your closing script tag. In addition, you've reverted to using "language" instead of "type" for your JS declaration - a bit outdated, which is why I showed you the newer syntax.

Do you not indent your code? It makes it so much easier to understand - not only for you, but for others (such as people here) to view.

Hope this helps,
Dan





Coedit Limited - Delivering standards compliant, accessible web solutions

[tt]Dan's Page [blue]@[/blue] Code Couch

http://www.codecouch.com/dan/

[/tt]

 

[BillyRayPreachersSon]

And make sure you are now calling "ccw" instead of "cc" in your HTML code.

Dan



Coedit Limited - Delivering standards compliant, accessible web solutions

[tt]Dan's Page [blue]@[/blue] Code Couch

http://www.codecouch.com/dan/

[/tt]

 

[BabyJeffy]

Try this...

var a = document.forms['WaterReadings'].[!]elements[/!]['CityWaterRollOver'].value;

Cheers,
Jeff

[tt]Jeff's Page @ Code Couch

http://www.codecouch.com/jeff/blog/

http://www.coedit.co.uk/

[/tt]

What is Javascript? FAQ216-6094

 

[BillyRayPreachersSon]

ideasworking,

Did you resolve your problem?

Dan



Coedit Limited - Delivering standards compliant, accessible web solutions

[tt]Dan's Page [blue]@[/blue] Code Couch

http://www.codecouch.com/dan/

[/tt]

 

[ideasworking]

Hi Dan,

Thank you very much for your help. Yes the problem is resolved. I'm sure the code could be optimized further... but at this point my focus is on creating a functioning script.

What I found was I needed to directly reference the state of the checkbox in the IF statement. For anyone who may try something like this in the future the code that worked for me is...

function ccw(){
   var PreviousValue = 771970    ;
   var frm = document.forms["WaterReadings"].elements;

   if (frm["CityWaterRollover"].checked) {
      if (frm["NewCityWaterReading"].value== PreviousValue) {
         frm["CityUsage"].value = frm["NewCityWaterReading"].value - PreviousValue;
      } else {
         frm["CityUsage"].value = frm["NewCityWaterReading"].value - PreviousValue + 1000000;
      }
   } else {
      frm["CityUsage"].value = frm["NewCityWaterReading"].value - PreviousValue;
   }
}

One more thing... I'm actually creating this code with PHP so that the variable PreviousValue changes dynamically. That code is as follows...

	echo "function ccw(){\n";
	echo "   var PreviousValue = ".$CW.";\n";
   	echo "   var frm = document.forms[\"WaterReadings\"].elements;\n";
	echo "\n";
	echo "   if (frm[\"CityWaterRollover\"].checked) {\n";
	echo "      if (frm[\"NewCityWaterReading\"].value== PreviousValue) {\n";
 	echo "         frm[\"CityUsage\"].value = frm[\"NewCityWaterReading\"].value - PreviousValue;\n";
	echo "      } else {\n";
	echo "         frm[\"CityUsage\"].value = frm[\"NewCityWaterReading\"].value - PreviousValue + 1000000;\n";
	echo "      }\n";
	echo "   } else {\n";
	echo "      frm[\"CityUsage\"].value = frm[\"NewCityWaterReading\"].value - PreviousValue;\n";
	echo "   }\n";
	echo "}\n";
	echo "\n";