Javascript

Question

正在做一个创建信用卡表格的练习，我有点卡住了。我的问题是它似乎总是关注第一个字段（名字），否则关注最后输入的字段。有没有一种简单的方法让它专注于产生错误的相应字段？

HTML:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Javascript Form Assignment</title>
</head>
<body bgcolor="E6E6FA">
<script src="./js/assignment.js">
</script>
<section>
<h2>Customer Details</h2>
<form name="contactForm" onsubmit="return validateForm()" method="post" >
 First Name
    <input id="fname" type="text" size="30">
 <br /><br />
 Last Name
    <input id="sname" type="text"  size="30">
 <br /><br />
 Postcode
 <input id="pcode" type="text" size="30">
 <br /><br />
 Email
 <input id="email" type="text" size="30">
 <br />
<h2>Payment Details</h2>
 Credit Card
 <select name="creditcard">
 <option value="amex">American Express</option>
 <option value="visa">Visa</option>
 <option value="master">Mastercard</option>
 </select>
 <br /><br />
 Card number 
    <input id="cardnum" type="text" size="30">
 <br /><br />
 CCV 
    <input id="ccv" type="text" size="30">
 <br /><br />
 Expiry MM/YYYY
 <select id="expiry_month" name="month">
 <option value="01">01</option>
 <option value="02">02</option>
 <option value="03">03</option>
 <option value="04">04</option>
 <option value="05">05</option>
 <option value="06">06</option>
 <option value="07">07</option>
 <option value="08">08</option>
 <option value="09">09</option>
 <option value="10">10</option>
 <option value="11">11</option>
 <option value="12">12</option>
 </select>
 <select id="expiry_year" name="year">
 <option value="2016">2016</option>
 <option value="2017">2017</option>
 <option value="2018">2018</option>
 <option value="2019">2019</option>
 <option value="2020">2020</option>
 </select>
 <br />
 <input type="submit" value="Submit"/> 
 <input type="button" value="Help" onclick="openWin()">
 <br />
</form>
</body>
</html>

还有我的Javascript：

function openWin() {
    window.open(src="./html/help.html");
}
function validateForm()
{
 var fname = document.getElementById("fname");
 var sname = document.getElementById("sname");
 var pcode = document.getElementById("pcode");
 var email = document.getElementById("email");
 var cardnum = document.getElementById("cardnum");
 var ccv = document.getElementById("ccv");
 
    var expiry_month = document.getElementById("expiry_month").value;
    var expiry_year = document.getElementById("expiry_year").value;

    var today = new Date();
    var selDate = new Date()
 
 if (fname.value==""){
  alert("Please enter your first name");
  fname.focus();
  return false;
 }
  if (sname.value==""){
  alert("Please enter your last name");
  fname.focus();
  return false;
 }
  if (pcode.value==""){
  alert("Please enter your postcode");
  fname.focus();
  return false;
 }
  if (pcode.value.length!=4 || isNaN(pcode.value)){
  alert("Please enter a 4 digit postcode");
  pcode.focus();
  return false;
 }
  if (email.value==""){
  alert("Please enter your email address");
  fname.focus();
  return false; 
 }
  if (email.value.indexOf("@")==-1){
  alert("Please enter a valid email address");
  email.focus();
  return false;
 }
 if (email.value.indexOf(".")==-1){
  alert("Please enter a valid email address");
  email.focus();
  return false;
 }
  if (cardnum.value==""){
  alert("Please enter your card number");
  fname.focus();
  return false; 
 }
  if (cardnum.value.length!=16 || isNaN(cardnum.value)){
  alert("Please enter a 16 digit credit card number");
  cardnum.focus();
  return false;
 }
  if (ccv.value==""){
  alert("Please enter your ccv");
  fname.focus();
  return false;
 }
 if (ccv.value.length!=3 || isNaN(ccv.value)){
  alert("Please enter a 3 digit CCV");
  ccv.focus();
  return false;
 }
    if (today.getTime() > selDate.setFullYear(expiry_year, expiry_month)){
        alert ("Expiry month and year is before today month and year.");
        return false;
 }
 
 alert("Thank you for your submission");
 return true;
}

抱歉这么久了 post，还在学习我的方法！

Answer 1

您的问题就在这里：

if (sname.value==""){
        alert("Please enter your last name");
        fname.focus();
        return false;
}

您正在检查姓氏字段，然后在名字字段无效时关注它。应该是这样的：

if (sname.value==""){
    alert("Please enter your last name");
    sname.focus();
    return false;
}

Javascript - 我如何专注于产生错误的领域？

Javascript - how do I focus to field producing an error?

html

field

focus