default values in functions

saimen · #1 09-08-2004, 02:13 AM

Hello

I would like to call a function with parameters, i.e. multiply('2','3','box1').
In this example, the first argument would be multiplied with the second and written into the div with the id="box1".

My question:
How can I set a default value for the third argument? => so if I call multiply('2','3') then it should automatically set the output-variable to 'box1' if not other defined in the call.

I'm sure that this is possible but I unfortunately can't find anything about default values neither in this forum nor with google...

Thank you for the answers,
saimen

HaganeNoKokoro · #2 09-08-2004, 02:24 AM

Code:

<html>
<head>
<title>function default</title>
<script type="text/javascript">
function add(a, b, id) {

  /* Here I set default values */
  if(!a) a=0;
  if(!b) b=0;
  if(!this.id) id="di1";
  /* End of default values */

  if(document.getElementById(id).childNodes.length==0) document.getElementById(id).appendChild(document.createTextNode(""));
  document.getElementById(id).firstChild.data=(a+b);
}
</script>
</head>
<body onload="add(1);">
<div id="di1"></div>
</body>
</html>

saimen · #3 09-08-2004, 02:46 AM

Hello
Thank you for your answer. I've tried to apply it for my function. There is good news and bad news for me:
good news: if targetDiv is not set, then it sets the value to "calendar". that's nice :o)
bad news: if targetDiv is set, it overwrites the value with "calendar".
=> I've used the alerts to give out the values before and after the default settings...

Maybe I'm making something wrong?!

Code:

function ShowCalendar(dateValue, sourceField, targetDiv) {
	//alert("Funktion ShowCalendar, Variable dateValue: "+dateValue);

	//set default variables for targetDiv
	alert("Funktion ShowCalendar, Variable targetDiv: "+targetDiv);
	if(!this.targetDiv) targetDiv="calendar";
	alert("Funktion ShowCalendar, Variable targetDiv: "+targetDiv);

javaNoobie · #4 09-08-2004, 05:07 AM

how are you calling this function? what are you passing to it?

saimen · #5 09-09-2004, 12:53 AM

The function ShowCalendar(dateValue, sourceField, targetDiv) is called from a link in html:

Code:

	<a href="#" onclick="ShowCalendar(document.forms['formular1'].elements['startdatum'].value, 'startdatum'); return false;">
	<img src="calendar.gif" alt="" border="0" />
	</a>

The values passed are (for example):
dateValue: "2004-09-01" (or empty)
sourceField: "startdatum" (never empty)
targetDiv: "calendar2" (or empty)

javaNoobie · #6 09-09-2004, 04:37 AM

remove the 'this.'

**Kor** · #7 09-09-2004, 06:34 AM

Your function has 3 parameters, but you passed only 2 on event handler...

lwc · #8 03-16-2010, 03:58 AM

You can't (well, at least shouldn't) use something like

Code:

if (!a)

because false is a valid value (e.g. add(false)). What you need is Javascript's equivalence of
PHP's isset.

I wish Javascript would just support function foobar($value = "default value") like in PHP...

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