商品添加和减少

</pre><pre name="code" class="javascript">/*更新价格*/function update_price(input_id) {    var _number = $("#" + input_id);    var amount = _number.val();    var new_amount = amount.replace(/[^0-9]/g,'');    new_amount = new_amount == '0' ? 1 : new_amount;    new_amount = new_amount >= 1000 ? 999 : new_amount;    _number.val(new_amount);    var price = parseFloat($("#price").val());    var point = new_amount * price;    $("#total_price").text(point.toFixed(2));}//增加数量function add_number(input_id){    var input = $("#" + input_id);    var _number = input.val();    input.val(++_number);    update_price(input_id);}//减少数量function minus_number(input_id){    var input = $("#" + input_id);    var _number = input.val();    _number = _number <= 2 ? 1 : --_number;    input.val(_number);    update_price(input_id);}