当键入不包含“ @”的文本（它是电子邮件检查器）时，我试图将文本框的边框设为红色。不幸的是，这不会发生。
我尝试使用包含新边框颜色的类，但不幸的是，似乎从未应用过此更改。
这是html和js代码：
<!DOCTYPE html>
<html>
<head>
<title>
Sign Up Page
</title>
<link rel="stylesheet" href="style.css" media="screen"/>
</head>
<body>
<script>
function validateForm() {
var x = document.forms["myForm"]["fname"].value;
if (x == "") {
alert("something must be filled out");
return false;
}
else if (!(x.includes("@")))
{
alert("you must have to filled value with @");
document.getElementById("nameT").style.color="red";
document.getElementById("fname").className = 'error';
return false;
}
}
</script>
<div class="ocean">
<div class="wave"></div>
<div class="wave"></div>
</div>
<h1>
<center>
Whale
</center>
</h1>
<div class="loginbox">
<h2>
Login
</h2>
<form name="myForm" onsubmit="return validateForm()"
method="post">
<p id="nameT"> email </p>
<input type="text" name="fname" placeholder="enter
email" onblur="validateForm()">
<p name="passT"> password </p>
<input type="text" name="name" placeholder="enter
password">
<br>
<input type="submit" value="Submit">
<br>
<a href="#">
Lost your password?
</a>
<br>
<a href="#">
Create an account
</a>
</form>
</div>
</body>
</html>
这是css代码：
html, body { height: 100%; }
body {
background:radial-gradient(ellipse at center, rgba(255,254,234,1)
0%, rgba(255,254,234,1) 35%, #ffffff 100%);
overflow: hidden;
}
.ocean {
height: 5%;
width:100%;
position:absolute;
bottom:0;
left:0;
background: #ffffff;
}
.wave {
background: url(https://s3-us-west-
2.amazonaws.com/s.cdpn.io/85486/wave.svg) repeat-x;
position: absolute;
top: -198px;
width: 6400px;
height: 198px;
animation: wave 7s cubic-bezier( 0.36, 0.45, 0.63, 0.53)
infinite;
transform: translate3d(0, 0, 0);
}
.wave:nth-of-type(2) {
top: -175px;
animation: wave 7s cubic-bezier( 0.36, 0.45, 0.63, 0.53) -.125s
infinite, swell 7s ease -1.25s infinite;
opacity: 1;
}
@keyframes wave {
0% {
margin-left: 0;
}
100% {
margin-left: -1600px;
}
}
@keyframes swell {
0%, 100% {
transform: translate3d(0,-25px,0);
}
50% {
transform: translate3d(0,5px,0);
}
}
.loginbox
{
width: 340px;
height: 360px;
background: #000;
color: #fff;
top: 50%;
left:50%;
position: absolute;
transform: translate(-50%, -50%);
box-sizing: border-box;
}
h2
{
margin: 0;
padding: 0 0 20px;
text-align: center;
font-size: 22px;
}
.loginbox input
{
width: 100%;
margin-bottom: 20px;
}
.loginbox input[type="text"], input[type="password"]
{
border: none;
border-bottom: 1px solid #fff;
background: transparent;
outline: none;
height: 40px;
color: #fff;
font-size: 16px;
}
.loginbox input[type="submit"]
{
border: none;
outline: none;
height: 48px;
background: #fb2525;
color: #fff;
font-size: 18px;
border-radius: 20px;
}
.loginbox input[type="submit"]:hover
{
cursor: pointer;
background: #ffc107;
color: #000;
}
.loginbox a
{
text-decoration: none;
font-size: 12px;
line-height: 20px;
color: darkgrey;
}
.loginbox p
{
margin: 0;
padding: 10px;
font-weight: bold;
}
.loginbox a:hover
{
color: #ffc107;
}
.error{
border:2px solid red;
}
如果未在电子邮件文本框中键入“ @”符号，则预期的输出是边框变为红色。实际结果没有这种效果，而是出现“无法将属性'className'设置为null”的错误。
最佳答案
您正在使用document.getElementById("fname")，但是没有名称为id的任何"fname"，因此将输入更新为
<input type="text" id="fname" name="fname" placeholder="enter
email" onblur="validateForm()">
将
getElementById更改为document.getElementById("fname").classList.add('error');
并将您的
.error类更改为.error{
border-bottom:2px solid red !important;
}