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up vote 1 down vote favorite

What I want is to store the sum for a database object with id 3. (see input tags below) I have many different id's with different values. The value in the sample below I want to store is 2.

Besides that I want to increase/decrease the value of sum[3] using a "+" and a "-" button with JavaScript. So I created a function called incr and decr to do that:

<script type="text/javascript">
function incr(what)
{
    alert(what);
    what.value ++;

    // rest of the function I left out, it works with a 'normal' name of the input tag
    //but I need to use the array
}    
</script>

how many?<input type="text" size="10" name="sum[3]" value="2" />
<input name="plus" type="button" value="+" onclick="incr(document.sum[3])" />
<input name="min" type="button" value="-" onclick="decr(document.sum[3])" />

I can't get it working, even the alert doesn't return a value. Anybody?

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1 Answer 1

up vote 4 down vote accepted

This is not the most elegant approach as it is using lots of inline code, but it solves your problem. What went wrong with your approach is that document.sum[3] is not the correct selector the the name="sum[3]" input

<script type="text/javascript">
function incr(what)
{

    what.value ++;
    alert(what.value);
    // rest of the function I left out, it works with a 'normal' name of the input tag
    //but I need to use the array
}    
</script>

how many?<input type="text" size="10" name="sum[3]" value="2" />
<input name="plus" type="button" value="+" onclick="incr(document.getElementsByName('sum[3]')[0])" />
<input name="min" type="button" value="-" onclick="decr(document.getElementsByName('sum[3]')[0])" />

You should consider using jQuery and refactoring the code with event handlers rather than using inline javascript.

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what is what.value ? –  dav Nov 11 '12 at 22:05
    
The value of <input type="text" size="10" name="sum[3]" value="2" />, in this case 2. –  David Müller Nov 11 '12 at 22:07
    
was not careful enough ! –  dav Nov 11 '12 at 22:09
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