Question

Passing variable names as parameters to a function

Asked by: JohnPullam

My javascript is still limited and I am getting an error message that tells me I don't understand something that's probably fairly basic.
 
I have 3 javascript statements that work fine inside an onclick and I want to make them into a function. The problem is that the function has to be called with the name of a field to be changed, and all the examples I have seen have the parameters as values, not as names of fields that can be changed. My current code is:
 
function IdentifyText(fieldname, text )
{
 document.fieldname.insertAdjacentText('afterBegin',String.fromCharCode(13));
 document.fieldname.focus();
 document.fieldname.insertAdjacentText('afterBegin',text);
 return;
 }
 
The intent is that "fieldname" is passed as a variable (e.g., UpdateLead.Comment), and the 3 statements operate upon whatever field is supplied (e.g., document.UpdateLead.Comment). But it seems that javascript doesn't understand it as a field name and instead is trying to operate on an object called document.fieldname that doesn't exist! The error says "document.fieldname is null or not an object".
 
I am probably missing something simple in syntax but just can't find an example anywhere to show me the right way to do it.

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Asked On
2003-07-26 at 07:58:08ID20691176
Tags

passing

,

variable

Topic

JavaScript

Participating Experts
3
Points
50
Comments
10

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Answers

 

by: GrinsPosted on 2003-07-26 at 08:51:50ID: 9011073

i recently learned this myself.
when you call the function, try onClick="IdentifyText(this); return false;" and remove the document. from each line in your function so that each line starts with fieldname.

fieldname.insertAdjacentText('afterBegin',String.fromCharCode(13));
fieldname.focus();
fieldname.insertAdjacentText('afterBegin',text);

hope this helps.

my first answer to a question, im so excited

 

by: MirFiyazPosted on 2003-07-26 at 08:54:35ID: 9011086

try this

e.g.
function IdentifyText(fieldname, text )
{
//your code goes here
}

<form name='form1'>
  <input type='text' name='t1'>
  <input type='button' name='b1' onClick='IdentifyText(this.form.t1,"myText")>
</form>

 

by: mplungjanPosted on 2003-07-26 at 10:20:13ID: 9011413

Grins: What a horrible idea

Just do either of these and see what is passed.

<html>
<head>
      <title>Untitled</title>
<script>
function IdentifyText1(fieldObject, text ) {
fieldObject.insertAdjacentText('afterBegin',String.fromCharCode(13));
fieldObject.focus();
fieldObject.insertAdjacentText('afterBegin',text);
return;
}
function IdentifyText2(fieldName, text ) {
document.forms[0].elements[fieldName].insertAdjacentText('afterBegin',String.fromCharCode(13));
document.forms[0].elements[fieldName].focus();
document.forms[0].elements[fieldName].insertAdjacentText('afterBegin',text);
return;
}
function IdentifyText3(fieldObject, text ) {
fieldObject.value+=String.fromCharCode(13);
fieldObject.focus();
fieldObject.value+=text;
return;
}

</script>
</head>

<body>
<form>
<textarea name="a1"></textarea>
<input type="button" onClick="IdentifyText1(this.form.a1, 'Hello there 1')" value="Hello 1">
<input type="button" onClick="IdentifyText2('a1', 'Hello there 2')" value="Hello 2">
<input type="button" onClick="IdentifyText3(this.form.a1, 'Hello there 3')" value="Hello 3">
</form>

</body>
</html>

 

by: mplungjanPosted on 2003-07-26 at 10:21:53ID: 9011422

PS: The reason it is wrong is that you need the form so
document.forms[0].elements[fieldName] will work

the reason it works without the document is that IE will search the complete document object for something resembling the vairable name... But it is only a coincidence it works

 

by: JohnPullamPosted on 2003-07-26 at 11:04:59ID: 9011643

I have rated Grins as the person who gave me a solution, even though I am inclined to wonder if mplungjan may be able to provide me a more elegant one.

Grins' solution worked, while I kept encountering errors when I tried the iterations suggested later.

Thanx for the help.

 

by: mplungjanPosted on 2003-07-26 at 19:36:30ID: 9013120

It works, it is not standard

 

by: mplungjanPosted on 2003-07-26 at 19:37:20ID: 9013124

You mean you got errors with my 3 suggestions??? They were tested....

 

by: JohnPullamPosted on 2003-07-27 at 05:09:04ID: 9014135

FYI, I worked harder to try to make your suggestions work and this is what happenned:

Identify1 seems to have worked.

Identify2 generated a run time error that said
 - - - - - - - - - - -     document.forms.0.elements[...] is null or not an object
(and please note that I coded it as forms[0] just like your example)

Identify3 added the text at the end of the string, not at the start.

I had hoped that your solution would work because ideally I'd like one that works for Netscape too (in case there are any Netscape users left), but it must place the text first and locate the cursor in the correct place or it is of no use.

 

by: mplungjanPosted on 2003-07-27 at 05:14:08ID: 9014148

There is no way to place the cursor in Netscape

However v3 will add text in netscape too.
and here is how to add it in the beginning

function IdentifyText3(fieldObject, text ) {
  fieldObject.value=text+'\n'+fieldObject.value;
  return;
}

I was not sure what the script actually did, sorry.
The above script will work in all browsers

 

by: mplungjanPosted on 2003-07-27 at 05:19:56ID: 9014163

and the return is not needed

function IdentifyText3(fieldObject, text ) {
 fieldObject.value=text+'\n'+fieldObject.value;
}

so if the text is in another field then all that is needed is is this:


<div align="center">
<form onSubmit="
this.a1.value=this.f1.value+'\n'+this.a1.value;
this.f1.focus();
this.f1.select();
return false">
<input type="text" name="f1" value=""><br>
<textarea name="a1"></textarea><br>
<input type="submit" value=" Add ">
</form>
</div>

which will add on enter too

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