[RESOLVED] Simple javascript fails...7

**ajajajak** · 01-21-2010 10:15 AM

hey,

Script

Code:

function berekening(){
	var beginkapitaal=document.getElementById("beginkapitaal").value;
	var intrest=document.getElementById("intrest").value;
	var aantal_jaar=document.getElementById("aantal_jaar").value;
	var eindkapitaal=document.getElementById("eindkapitaal").value;

	eindkapitaal=beginkapitaal*Math.pow((1+intrest),aantal_jaar);
}

HTML

HTML Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Interestformulier</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript">
/* <![CDATA[ */
function berekening(){
	var beginkapitaal=document.getElementById("beginkapitaal").value;
	var intrest=document.getElementById("intrest").value;
	var aantal_jaar=document.getElementById("aantal_jaar").value;
	var eindkapitaal=document.getElementById("eindkapitaal").value;

	eindkapitaal=beginkapitaal*Math.pow((1+intrest),aantal_jaar);
}
/* ]]> */
</script>
</head>
<body>
<form action="">

	<table border="1" cellpadding="5">
		<thead>
			<tr>
				<th>Beginkapitaal</th>
				<th>Intrest</th>
				<th>Aantal jaar</th>
				<th>Eindkapitaal</th>
			</tr>
		</thead>		
		<tbody>
			<tr>
				<td><input type="text" id="beginkapitaal" name="beginkapitaal" /></td>
				<td><input type="text" id="intrest" name="intrest" onblur="if(document.getElementById('intrest').value>=1) document.getElementById('intrest').value=document.getElementById('intrest').value/100;"/></td>
				<td><input type="text" id="aantal_jaar" name="aantal_jaar" /></td>
				<td><input type="text" id="eindkapitaal" name="eindkapitaal" onselect="blur()" /></td>
			</tr>
		</tbody>
	</table>
	
	<p>
		<input type="button" value="Bereken eindkapitaal" onclick="berekening()" />
		<input type="reset" value="Opnieuw beginnen" />
	</p>
	
</form>

</body>
</html>

The goal is to display the value outputted by the function berekening() in the input field with the id="eindkapitaal".
Although the script does put out a value I do not succeed in getting it to show up in the textfield. Any suggestions/idea's why this is?

**skywalker2208** · 01-21-2010 10:19 AM

Change your function to this

HTML Code:

function berekening(){
	var beginkapitaal=document.getElementById("beginkapitaal").value;
	var intrest=document.getElementById("intrest").value;
	var aantal_jaar=document.getElementById("aantal_jaar").value;
	document.getElementById("eindkapitaal").value = beginkapitaal*Math.pow((1+intrest),aantal_jaar);
}

**ajajajak** · 01-21-2010 10:27 AM

It works but why does this differ from assigning that line to a variable first and afterwards calling on the variable to put a value in it?

thank you!

**skywalker2208** · 01-21-2010 10:43 AM

If you wanted to call it later you could have done

HTML Code:

var eindkapitaal=document.getElementById("eindkapitaal");	
eindkapitaal.value = beginkapitaal*Math.pow((1+intrest),aantal_jaar);

**ajajajak** · 01-21-2010 10:52 AM

I know but for some reason I thought you could store an attribute in a variable...whereas you can only store the value of that attribute and not the attribute itself.

**skywalker2208** · 01-21-2010 11:02 AM

Originally Posted by ajajajak

I know but for some reason I thought you could store an attribute in a variable...whereas you can only store the value of that attribute and not the attribute itself.

Storing it like

HTML Code:

var eindkapitaal=document.getElementById("eindkapitaal");

stores the object in eindkapitaal and then you are able to access its properties and methods.

If you use your example

HTML Code:

var eindkapitaal=document.getElementById("eindkapitaal").value;

it means you are storing the actual value of it. You can look at it as calling a function that returns a result and storing it in your variable. You can't call that function through your variable again.

**ajajajak** · 01-21-2010 11:20 AM

Ok that makes sense.

I suspected it was something like that. Thank you for clarifying!

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