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爲什麼驗證用戶名時jQuery/JavaScript（classname或id）.value.length不起作用？
document.getElementById("button1").addEventListener("click", mouseOver1);
function mouseOver1(){
document.getElementById("button1").style.color = "red";
}
document.getElementById("button2").addEventListener("click", mouseOver);
function mouseOver(){
document.getElementById("button2").style.color = "purple";
}
$("#button1").hover(function() {
$(this).css('cursor','pointer');
});
$("#button2").hover(function() {
$(this).css('cursor','pointer');
});
$('#button1').on('click', function() {
var error = 0;
var usernameError = document.getElementById("username_error1");
var passwordError = document.getElementById("password_error2");
if ($(".existingUsername").get(0).value != "S0104675") {
usernameError.innerHTML = "Please enter an existing valid username";
error = 1;
} else {
usernameError.innerHTML = '';
}
if ($(".existingPassword").get(0).value != "honor433") {
passwordError.innerHTML = "Please enter an existing valid password";
error = 1;
} else {
passwordError.innerHTML = '';
}
if(error == 0)
{
$("#para1").animate({ left: "-100%" });
$(".username-label").animate({ left: "-105%" });
$(".existingUsername").animate({ left: "-105%" });
$(".password-label").animate({ left: "-105%" });
$(".existingPassword").animate({ left: "-105%" });
$("#button1").animate({ left: "-105%" });
}
});
$('#button2').on('click', function() {
var newUsernameError = $("#New_Username_error").html('');
var newPasswordError = $("#New_Password_error").html('');
var newEmailAddressError = $("#New_Email_error").html('');
var newRepeatEmailAddressError = $("#Repeat_Email_error").html('');
// just to make the later conditions easier to read, let's grab all the values into vars:
var newUsername = $('.newUsername').val();
var newPassword = $('.newPassword').val();
var newEmail = $('.newEmail').val();
var repeatEmail = $('.repeatEmail').val();
var errorsFound = false;
if (newUsername === "") {
errorsFound = true;
newUsernameError.html("The username must not be empty.");
} else if (newUsername.length < 6) {
errorsFound = true;
newUsernameError.html("The username must be at least 6 characters.");
}
if (newPassword.length < 6) {
errorsFound = true;
newPasswordError.html("The password must be at least 6 characters.");
}
if (newEmail === "") {
errorsFound = true;
newEmailAddressError.html("The email must not be left empty.");
} else if (!/@/.test(newEmail)) {
errorsFound = true;
newEmailAddressError.html("The email must contain an @ symbol.");
}
if (repeatEmail !== newEmail) {
errorsFound = true;
newRepeatEmailAddressError.html("This repeat email doesn't equal to the first one entered.");
}
});.intro h1 {
font-family: 'Cambria';
font-size: 16pt;
font: bold;
text-align: left;
}
.intro p {
font-family: 'Calibri';
font: italic;
font-size: 12pt;
padding: 0px 690px 0px 20px;
text-align: left;
}
.content {
border: 2px solid;
-webkit-border-radius: 10px;
-moz-border-radius: 10px;
border-radius: 10px;
}
#para1 {
padding: 0px 1050px 0px 20px;
position: relative;
}
#para2 {
padding: 0px 1099px 0px 20px;
position: relative;
}
.username-label,
.password-label {
margin: 10px 0px 0px 350px;
position: relative;
top: -70px;
}
.existingUsername,
.existingPassword,
#username_error1,
#password_error2
{
top: -70px;
position: relative;
}
#button1{
background-color: #add8e6;
margin-left: 425px;
position: relative;
top: -70px;
-webkit-border-radius: 10px;
-moz-border-radius: 10px;
border-radius:10px;
padding: 0px 20px 0px 20px;
}
#button2{
background-color: #add8e6;
margin-left: -500px;
position: relative;
top: -30px;
-webkit-border-radius: 10px;
-moz-border-radius: 10px;
border-radius: 10px;
padding: 0px 20px 0px 20px;
}
.Username-label1,
.Password-label2,
.Email-label3,
.Repeat-Email-label4
{
margin: 0px 0px 0px 330px;
position: relative;
top: -70px;
}
.newUsername,
.newPassword,
.newEmail,
.repeatEmail{
position: relative;
top: -70px;
margin-left: 40px;
}
span{
color: red;
margin-left: 300px;
position: relative;
top: -60px;
}<html>
<head>
<link href="Home.css" rel="stylesheet" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<title>Project</title>
</head>
<body>
<div class="container">
<div class="intro">
<h1>Welcome to Cuyahoga Community College Student Services Online</h1>
<p>Cuyahoga Community College recognizes students' rights to access personal and academic records in accordance with the Family Educational Rights and Privacy Act of 1974 (FERPA) as amended by Public Law 93-568.</p>
</div>
<br/>
<div class="content">
<div class="row top">
<p id="para1">Already have an account with us? Returning users may log in by entering their site username and password. </p>
<div class="login">
<label class="username-label" for="existingUsername">Username</label>
<input class="existingUsername" type="text" /><br><span id="username_error1"></span><br>
<label class="password-label" for="existingPassword">Password</label>
<input class="existingPassword" type="password"/><br><span id="password_error2"></span><br>
<button id="button1">Log in</button>
</div>
</div>
<hr/>
<div class="row bottom">
<p id="para2">New users, please create a new account by providing us with some basic information.</p>
<div class= "new_customers_info">
<label class="Username-label1" for="newUsername">Username</label>
<input class="newUsername" type="text"/><br><span id="New_Username_error"></span><br>
<label class="Password-label2" for="newPassword">Password</label>
<input class="newPassword" type="password"/><br><span id="New_Password_error"></span><br>
<label class="Email-label3" for="newEmail">Email Address</label>
<input class="newEmail" type="email"/><br><span id="New_Email_error"></span><br>
<label class="Repeat-Email-label4" for="repeatEmail">Repeat Email Address</label>
<input class="repeatEmail" type="email"/><span id="NewReenter_Email_error"></span>
<button id="button2">Create Account</button>
</div>
</div>
</div>
<br/>
<footer>Cuyahoga Community College</footer>
<footer>700 Carnegie Avenue, Cleveland, Ohio, 44115</footer>
</div>
<script src="Home.js"></script>
</body>
</html>我工作的驗證（下部）文本框，並試圖驗證用戶名文本框時，我遇到了一個問題。例如，在value.length（我改變了長度）在我的第一個條件。
當我點擊'創建一個帳戶'按鈕，它不會做任何事情（我知道它現在不應該做任何事情，只要用戶名至少是6個字符，但是當我做className或Id.length它的工作原理），但由於某種原因，它顯示錯誤消息，即使我在文本框中有正確的單詞長度或更多。
這是我的代碼。
爲了幫助我們更好地爲您提供幫助，請刪除與您遇到的問題無關的所有示例代碼。嘗試並確保您的示例是最小，完整和可驗證的：http://stackoverflow.com/help/mcve – Hamms
也避免將純js與jquery結合使用 – guradio
爲什麼要混合使用jquery和DOM？選擇一個，並堅持下去 – epascarello