http://jsfiddle.net/stofke/gukh2
Я надеюсь, что это не то, что вы хотите, потому что, если кто-то еще покупает товар, в то время как другой человек делает то же самое, JavaScript не будет иметь точное количество предметов.Это не похоже на работу только с javascript.
HTML
<div id="navcontainer">
<ul id="navlist">
<li><a href="#" class="current">Item one</a></li>
<li><a href="#">Item two</a></li>
<li><a href="#">Item three</a></li>
<li><a href="#">Item four</a></li>
<li><a href="#">Item five</a></li>
</ul>
</div>
<div class="box">
<h2>Stock</h2>
<select id="myStock" size="5" width="50px">
<option></option>
</select>
</div>
<div class="box">
<h2>Cart</h2>
<select id="myCart" size="5" width="50px">
<option></option>
</select>
</div>
<br class="clear"/>
<h2>The effect on the items object (unaffected)</h2>
<span id="items"></span>
<h2>The effect on the stock object</h2>
<span id="stock"></span>
<h2>The effect on the cart object</h2>
<span id="cart"></span>
CSS
a {
font: bold 100% "Lucida Grande", Lucida, Verdana, sans-serif;
}
#navlist li
{
display: inline;
list-style-type: none;
padding-right: 5px;
}
#navlist li a.current
{
font-weight: bold;
}
h2
{
text-decoration: underline;
color: #555;
font: bold 120% "Lucida Grande", Lucida, Verdana, sans-serif;
margin-top:30px;
margin-bottom:15px;
}
.box {
float:left;
margin-left:5px;
}
.clear {
clear:both;
}
JavaScript
$(function() {
var stockItems ={"Item one":2,"Item two":5,"Item three":9,"Item four":13,"Item five":14};//stock object
var cartItems ={"Item one":0,"Item two":0,"Item three":0,"Item four":0,"Item five":0};//cart object
var originalItems ={"Item one":2,"Item two":5,"Item three":9,"Item four":13,"Item five":14};//items object
$("#navlist li a").click(function() {
$("#myStock option").remove(); //reset the stock dropdownlist on click
$("#myCart option").remove(); //reset the cart dropdownlist on click
var itemName; //name of the item
var total_stockItems = stockItems[$(this).text()]; //get total stockitems for an item
var total_cartItems = cartItems[$(this).text()]; //get total cartitems for an item
if (total_cartItems < originalItems[$(this).text()]) {//total amount of cartitems for an item has to be lower than the initial amount for that item, you can't buy more than there is.
cartItems[$(this).text()] += 1; //counter, updates the cart-object +1
}
if (total_stockItems > 0) {//total amount of stockitems for an item has to be higher than 0 for to be able to add it to the cart
stockItems[$(this).text()] -= 1; //counter, updates the stock-object -1
}
for (itemName in (stockItems)) {
if (stockItems.hasOwnProperty(itemName)) {
$("#myStock").append($("<option></option>").val(stockItems[itemName]).html(itemName + ": " + stockItems[itemName] + " piece(s) in stock")); //build the stock dropdown
}
}
for (itemName in (cartItems)) {
if (cartItems.hasOwnProperty(itemName)) {
$("#myCart").append($("<option></option>").val(cartItems[itemName]).html(itemName + ": " + cartItems[itemName] + " piece(s) in cart")); //build the cart dropdown
}
}
//some info on the objects
$("#items").text("var items =" + JSON.stringify(originalItems) + ";"); //output the items object
$("#stock").text("var stock =" + JSON.stringify(stockItems) + ";"); //output the current stock object
$("#cart").text("var cart =" + JSON.stringify(cartItems) + ";"); //output the current car object
return false;
});
});