我的表格如下。我想我已经正确地从输入文本字段中获取了值。但是当我alert()它时，它什么也没有显示出来。 （甚至不是空的）
以下表格：
var firstName = document.getElementById('firstName').value;
var lastName = document.getElementById('lastName').value;
var email = document.getElementById('email').value;
$("#validationAlert").hide();
$("#btn-sign-up").click(function showAlert() {
if (firstName == "") {
$("#firstName").focus();
alert(firstName); //this shows nothing even when I type something
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function() {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (lastName == "") {
$("#lastName").focus();
alert("2");
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function() {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (email == "") {
document.getElementById('email').focus();
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function() {
$("#validationAlert").slideUp(1500);
});
return false;
}
return true;
});<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<form method="POST" action="Login" onsubmit="return(showAlert());">
<div class="form-group md-form">
<!--<input type="email" class="form-control" id="email" value="" placeholder="Enter email address">-->
<i class="fa fa-pencil prefix grey-text"></i>
<input type="text" id="firstName" class="form-control">
<label for="defaultForm-email">First Name</label>
</div>
<div class="form-group md-form">
<!--<input type="email" class="form-control" id="email" value="" placeholder="Enter email address">-->
<i class="fa fa-pencil prefix grey-text"></i>
<input type="text" id="lastName" name="lastname" class="form-control">
<label for="defaultForm-email">Last Name</label>
</div>
<div class="form-group md-form">
<!--<input type="email" class="form-control" id="email" value="" placeholder="Enter email address">-->
<i class="fa fa-envelope prefix grey-text"></i>
<input type="email" id="email" name="email" class="form-control">
<label for="defaultForm-email">Email Address</label>
</div>
<div class="text-center">
<button type="reset" class="btn btn-amber btn-sm"><strong>Reset</strong></button>
<!--<button type="submit" id="btn-sign-in" class="btn btn-green btn-sm"><strong>Sign in</strong></button>-->
<button type="submit" id="btn-sign-up" class="btn btn-green btn-sm"><strong>Sign Up</strong></button>
</div>
</form>
谁能告诉我哪里出错了？
答案 0 :(得分：1)
您的情况表明，如果您的名字，姓氏和电子邮件都是空的，则只会执行警报代码。
可能你需要以其他方式检查你的情况，
transformData()等
答案 1 :(得分：0)
最后，我找到了自己的错。单击按钮后（而不是之前），应检查我输入/不输入的值。所以script应该是这样的。
<script>
$("#validationAlert").hide();
$("#btn-sign-up").click(function showAlert() {
var firstName = document.getElementById('firstName').value;
var lastName = document.getElementById('lastName').value;
var email = document.getElementById('email').value;
var userName = document.getElementById('username').value;
var password = document.getElementById('password').value;
var repeatPassword = document.getElementById('repeatpassword').value;
var securityQuestion = document.getElementById('securityQuestion').value;
var answer = document.getElementById('answer').value;
if (firstName == "") {
// alert("URL is mandatory!");
$("#firstName").focus();
alert(firstName);
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (lastName == "") {
$("#lastName").focus();
alert("2");
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (email == "") {
document.getElementById('email').focus();
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (userName == "") {
document.getElementById('username').focus();
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (password == "") {
document.getElementById('password').focus();
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (repeatPassword == "") {
document.getElementById('repeatpassword').focus();
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (securityQuestion == "-1") {
document.getElementById('securityQuestion').focus();
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
} else if (answer == "") {
document.getElementById('answer').focus();
$("#validationAlert").fadeTo(2000, 500).slideUp(500, function () {
$("#validationAlert").slideUp(1500);
});
return false;
}
return true;
});
</script>