I've been posting some questions mainly about fields lateley and i've gotten good respons.

But theres one more thing I need to learn how to do:

I need to have have two links that add and subtract 1 to the value of a text field.
I'm gonna need to do this many times so a function would be best.

This is what I have:

Script:
var fieldname;
function add(fieldname) {
document.forms[0].fieldname.value++ ;
}

Html:
<input type="text" name="ABC" value="0">
<a href="javascript:add(ABC)">plus</a>

But it just doesnt work.

Originally Posted by oreoT

I've been posting some questions mainly about fields lateley and i've gotten good respons.

But theres one more thing I need to learn how to do:

I need to have have two links that add and subtract 1 to the value of a text field.
I'm gonna need to do this many times so a function would be best.

This is what I have:

Script:
var fieldname;
function add(fieldname) {
document.forms[0].fieldname.value++ ;
}

Html:
<input type="text" name="ABC" value="0">
<a href="javascript:add(ABC)">plus</a>

But it just doesnt work.

You should give your text box an "id" attribute, so you can use document.getElementById() in the add() function:

function add(field)
{
    field = document.getElementById(field);

Now you can get the field's value, but since it's a text box, the script will see the value as a string, not a number. That's why this line:

document.forms[0].fieldname.value++ ;

doesn't work in your original function. You need to use parseInt() to get an integer value from a string:

function add(field)
{
    field = document.getElementById(field);	
    val = parseInt(field.value);

I'm not really sure why, but the ++ syntax isn't going to work, you need to use +=

function add(field)
{
    field = document.getElementById(field);	
    val = parseInt(field.value);
    val += 1;

Now that you've read the value, turned it into a number, and added one to it, you just need to set the field to the new value:

function add(field)
{
    field = document.getElementById(field);	
    val = parseInt(field.value);
    val += 1;
    field.value = val;
}

And the HTML can be something like this:

<input type="text" name="ABC" id="ABC" value="0"> 
<a href="#" onclick="add('ABC');">+</a> 
<a href="#" onclick="subtract('ABC');">-</a> 

Oh, and when passing "ABC" to the function add(), you need to use quotes around 'ABC' otherwise the script thinks you're passing it an object.

Thanks, I got it working. I didn't need to set the ID, the name was enough.

Also I was trying to make one field be the sum of all the other fields.
So field A would have the value of field 1,2,3,4,5 and so on.

Is there a good way to do this, in a way that the value of field A automatically updates when there is a change in value in the fields 1,2,3,... ?