jQuery Count Totals

Here's a solution: http://jsfiddle.net/AlexCode/ZzYHt/2/

I picked RainerJ code as it's the one marked as accepted solution.
Be aware that on RainerJ's original code, the variable fieldName is declared twice without the var before.
This makes it a global scope variable which is not good.
In my code I fixed that also.

Probably this is not the code exactly that you're using but you can also improve it and it might be more or less important depending on the amount of elements that you have on the page.

Here's the full code as a reference.
I only added the Total element on the HTML and changed the javascript as necessary.
The processTotal() function is being called at the end so that the total is displayed upon page_load.

HTML

<form id='myform' method='POST' action='#'>
    <input type='button' value='-' class='qtyminus' field='quantity1' />
    <input type='text' id='quantity1' value='0' class='qty' />
    <input type='button' value='+' class='qtyplus' field='quantity1' />
    <br/>
    <input type='button' value='-' class='qtyminus' field='quantity2' />
    <input type='text' id='quantity2' value='4' class='qty' />
    <input type='button' value='+' class='qtyplus' field='quantity2' />
    <br/>
    <input type='button' value='-' class='qtyminus' field='quantity3' />
    <input type='text' id='quantity3' value='99' class='qty' />
    <input type='button' value='+' class='qtyplus' field='quantity3' />
    <br/>
    
    <span>Total: </span><span id="total">--</span>
</form>

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Javascript

jQuery(document).ready(function () {
    // This button will increment the value
    $('.qtyplus').click(function (e) {
        // Stop acting like a button
        e.preventDefault();
        // Get the field name
        var fieldName = $(this).attr('field');
        // Get its current value
        var currentVal = parseInt($('#' + fieldName).val());
        // If is not undefined
        if (!isNaN(currentVal)) {
            // Increment
            $('#' + fieldName).val(currentVal + 1);
        } else {
            // Otherwise put a 0 there
            $('#' + fieldName).val(0);
        }
        
        $('#' + fieldName).trigger('change');
    });
    // This button will decrement the value till 0
    $(".qtyminus").click(function (e) {
        // Stop acting like a button
        e.preventDefault();
        // Get the field name
        var fieldName = $(this).attr('field');
        // Get its current value
        var currentVal = parseInt($('#' + fieldName).val());
        // If it isn't undefined or its greater than 0
        if (!isNaN(currentVal) && currentVal > 0) {
            // Decrement one
            $('#' + fieldName).val(currentVal - 1);
        } else {
            // Otherwise put a 0 there
            $('#' + fieldName).val(0);
        }
        
        $('#' + fieldName).trigger('change');
    });
    
    $('input.qty').on('change', function() {
        processTotal();
    });
    
    function processTotal() {
        var total = 0;
        $('input.qty').each(function(idx, item) {
            total += isNaN(item.value) ? 0 : parseInt(item.value);
        });
        
        $('#total').html(total);
    }
    
    processTotal();
});

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CSS

.qty {
    width: 40px;
    height: 25px;
    text-align: center;
}
input.qtyplus {
    width:25px;
    height:25px;
}
input.qtyminus {
    width:25px;
    height:25px;
}

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