你好堆栈Overflowers。我的HTML课程中有一个正在进行的作业。我目前已经为它创建了4个简单的介绍页面，但目前仍然坚持这个非常简单的JavaScript计算。但我觉得我很亲近。请原谅我凌乱的代码。我绝对是JS中的“noob”一词，但我正在努力。任何帮助表示赞赏。
我的提示是：“创建一个页面，允许从一个短列表中选择一个设备，然后允许选择租赁开始日期和结束日期，然后计算两个选定日期之间的天数。最后，乘以单位租金以天数计算的成本，并为总成本增加8％的税。“
我的代码：
<html>
<head>
<title> Rental Program </title>
<script language="javascript">
//listbox.htm
function processit() {
string1=document.myform.numb1.value;
numb2=document.myform.alist.selectedIndex;
perweek=0;
if (string1 == 'Books') { perweek=300; }
if (string1 == 'Calculator') { perweek=200; }
if (string1 == 'Computer') { perweek=100; }
if (string1 == 'Camera') { perweek= 50; }
}
</script>
</head>
<body
<form name=myform>
<h4>Enter the item you wish to rent using the list below:
<input size =12 type="text" name="numb1">
</h4>
<li> Books = $300 per week
<li> Calculator = $200 per week
<li> Computer = $100 per week
<li> Camera = $50 per week
<h4> Select how many weeks you wish to rent: </h4>
<p>
</form>
</body>
<html>
<head>
<script type="text/javascript">
function GetDays(){
var dropdt = new Date(document.getElementById("drop_date").value);
var pickdt = new Date(document.getElementById("pick_date").value);
return parseInt((dropdt - pickdt) / (24 * 3600 * 1000));
}
function cal(){
if(document.getElementById("drop_date")){
document.getElementById("numdays2").value=GetDays();
}
function GetTotal(){
var total = ($('[numb1]').val()(*0.8*total));
}
</script>
</head>
<body>
<div id="reserve_form">
<div id="pickup_date"><p><label class="form">Pickup Date:</label><input type="date" class="textbox" id="pick_date" name="pickup_date" onchange="cal()"</p></div>
<div id="dropoff_date"><p><label class="form">Dropoff Date:</label><input type="date" class="textbox" id="drop_date" name="dropoff_date" onchange="cal()"/></p></div>
<div id="numdays"><label class="form">Number of days:</label><input type="text" class="textbox" id="numdays2" name="numdays"/></div>
<h5>Total Amount in $ </h5>
<input size =12 type="text" name="total">
<p>
</div>
</body>
</html>第70行出错。您也忘了终止if语句
if(document.getElementById("drop_date")){
工作代码：
<html>
<head>
<title> Rental Program </title>
<script src="https://code.jquery.com/jquery-1.11.3.js"></script>
<script language="javascript">
//listbox.htm
function processit() {
string1=document.getElementById("numb1").value;
//numb2=document.myform.alist.selectedIndex;
perweek=0;
if (string1 == 'Books') { perweek=300; }
if (string1 == 'Calculator') { perweek=200; }
if (string1 == 'Computer') { perweek=100; }
if (string1 == 'Camera') { perweek= 50; }
return perweek
}
</script>
</head>
<body
<form name=myform>
<h4>Enter the price of the item you wish to rent using the list below:
<input size =12 type="text" name="numb1" id="numb1">
</h4>
<li> Books = $300 per week
<li> Calculator = $200 per week
<li> Computer = $100 per week
<li> Camera = $50 per week
<h4> Select how many weeks you wish to rent: </h4>
<p>
</form>
</body>
<html>
<head>
<script type="text/javascript">
var items = {
"Book":"300"
}
function GetDays(){
var dropdt = new Date(document.getElementById("drop_date").value);
var pickdt = new Date(document.getElementById("pick_date").value);
return parseInt((dropdt - pickdt) / (24 * 3600 * 1000));
}
function cal(){
if(document.getElementById("drop_date")){
var result = GetDays()
if(isNaN(result)){result="Please fill out both dates"}
document.getElementById("numdays2").value=result;
}
}
function GetTotal(){
var price = processit(document.getElementById("numb1").value)
var duration = document.getElementById("numdays2").value
var total = Math.floor((price*(0.8*(duration)))*100)/100;
if(isNaN(total)){total="Please fill out both dates"}
document.getElementById("total").value = total
}
</script>
</head>
<body>
<div id="reserve_form">
<div id="pickup_date"><p><label class="form">Pickup Date:</label><input type="date" class="textbox" id="pick_date" name="pickup_date" onchange="cal();GetTotal()"/></p></div>
<div id="dropoff_date"><p><label class="form">Dropoff Date:</label><input type="date" class="textbox" id="drop_date" name="dropoff_date" onchange="cal();GetTotal()"/></p></div>
<div id="numdays"><label class="form">Number of days:</label><input type="text" class="textbox" id="numdays2" name="numdays" disabled/></div>
<h5>Total Amount in $ </h5>
<input size =12 type="text" name="total" id="total" disabled>
<p>
</div>
</body>
</html>