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Thread: default values in functions

  1. #1
    Join Date
    Sep 2004
    Posts
    3

    Question default values in functions

    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

  2. #2
    Join Date
    Jul 2004
    Location
    Canada, eh
    Posts
    784
    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>

  3. #3
    Join Date
    Sep 2004
    Posts
    3

    Post

    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);

  4. #4
    Join Date
    Jul 2004
    Location
    Singapore, SG
    Posts
    654
    how are you calling this function? what are you passing to it?

  5. #5
    Join Date
    Sep 2004
    Posts
    3
    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)

  6. #6
    Join Date
    Jul 2004
    Location
    Singapore, SG
    Posts
    654
    remove the 'this.'

  7. #7
    Join Date
    Dec 2003
    Location
    Bucharest, ROMANIA
    Posts
    15,428
    Your function has 3 parameters, but you passed only 2 on event handler...

  8. #8
    Join Date
    Mar 2010
    Posts
    14
    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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