[devote]

<div class="oneItem" id="product_1"> 
    <div class="imageItem"></div> 
    <div class="infoItem"> 
        <p>Цена:&nbsp;<span class="priceItem">44.34</span>руб.</p> 
        <span> 
            Кол-во:&nbsp; 
            <span class="rateItem" onclick="rateChange( 1, 1 );">◄</span> 
            <input class="rateInput" type="text" value="1" />
            <input class="priceForOne" type="hidden" value="44.34" />
            <span class="rateItem" onclick="rateChange( 1, 0 );">►</span> 
        </span> 
        <input type="submit" value="Добавить в корзину" /> 
    </div> 
</div>
<div class="oneItem" id="product_2"> 
    <div class="imageItem"></div> 
    <div class="infoItem"> 
        <p>Цена:&nbsp;<span class="priceItem">68.30</span>руб.</p> 
        <span> 
            Кол-во:&nbsp; 
            <span class="rateItem" onclick="rateChange( 2, 1 );">◄</span> 
            <input class="rateInput" type="text" value="2" />
            <input class="priceForOne" type="hidden" value="34.15" />
            <span class="rateItem" onclick="rateChange( 2, 0 );">►</span> 
        </span> 
        <input type="submit" value="Добавить в корзину" /> 
    </div> 
</div>

<script type="text/javascript">
function getElemsByClass( className, context ) {

	var nodeList = [];
	context = context || document;

	if ( context.getElementsByClassName ) {
		nodeList = Array.prototype.slice.call(
			context.getElementsByClassName( className )
		);
	} else {
		var elems = context.getElementsByTagName("*"),
			classMatch = new RegExp('(?:^| +)' + className + '(?: +|$)');

		for( var elem, i = 0 ; elem = elems[ i ]; i++ ) {
			if ( classMatch.test( elem.className ) ) {
				nodeList.push( elem );
			}
		}
	}

	return nodeList;
}

function rateChange( product_id, type ) {
	var product = document.getElementById( 'product_' + product_id );
		rateInput = getElemsByClass( 'rateInput', product ),
		priceForOne = getElemsByClass( 'priceForOne', product ),
		priceItem = getElemsByClass( 'priceItem', product ),
		count = parseInt( rateInput[ 0 ].value ),
		price = parseFloat( priceForOne[ 0 ].value );

	count = type == 0 ? ++count : --count;
	rateInput[ 0 ].value = count;
	priceItem[ 0 ].innerHTML = ( price * count ).toFixed( 2 );
}

</script>