初学者尝试在使用javascript提交之前学习有关验证字段的信息 [英] Beginner trying to learn about validating fields before submit in javascript
本文介绍了初学者尝试在使用javascript提交之前学习有关验证字段的信息的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
有人可以帮我吗?我试图在提交之前验证字段，如果字段为空，我需要显示错误消息.我已经尝试过jQuery，但是我想学习JavaScript方式.我整天都在努力！首先尝试使广告图像向下滑动，然后在单击退出按钮后消失/淡入淡出.接下来又是4个小时，试图获取加号和减号图标来更改和滑动登录表单.现在我必须验证！请帮助大声笑
Can someone please help me? I am trying to get the fields validated before submit and if fields are empty I need error message to show up. I have tried jquery but i want to learn the javascript way. I have been working on this all day! Started with trying to get the ad image to slide down then disappear/fade after clicking the exit button. Followed with another 4 hours trying to get the plus and minus icons to change and slide the login form. Now I MUST VALIDATE! please help lol
<script>
//Fading in Advertisent
$(document).ready(function() {
$("#ad").animate({
top: '100px',
}, (5000));
//Closing The Advertisement
$("#adbtn").click(function() {
$("#ad").fadeOut(5000);
});
$(".plus").click(function() {
$("form").slideToggle(1000); // half second duration
$(this).toggleClass("plus").toggleClass(
"minus");
var userName = document.getElementById(
"username").value;
var password = document.getElementById(
"pw").value;
//Error Variables_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
var milesDrivenError = document
.getElementById("error");
var gallonsUsedError = document
.getElementById("error");
//Clear out error messages eveerytime
milesDrivenError.firstChild.nodeValue =
"";
gallonsUsedError.firstChild.nodeValue =
"";
//**********************************************************
// Step 3: check for valid username
// if (not a number),
// write an error message to the form
// using the miles_driven_error id
//**********************************************************
if (isNaN(userName) || userName <=
0) {
milesDrivenError.firstChild
.nodeValue =
"Please Enter A Valid Username";
return false;
} //end if
//**********************************************************
// Step 4: check for valid gallons used
// if (not a number OR gallons used < 0),
// write an error message to the form
// using the gallons_used_error id
//**********************************************************
if (isNaN(password) || password <=
0) {
gallonsUsedError.firstChild
.nodeValue =
"Please Enter A Valid Password";
return false;
} //end if
function formSubmit() {
document.getElementById(
"form").submit();
document.getElementById(
"error").firstChild
.nodeValue = "";
}
//**********************************************************
// Step 9: define an anonymous function for window.onload
// This function should assign the event handler
// functions for the Calculate and Clear buttons
//**********************************************************
function init() {
document.getElementById(
"button").onclick =
formSubmit;
}
window.onload = init;
var frm = document.querySelector(
'form'),
user = document.querySelector(
'#username'),
pwd = document.querySelector(
'#pw'),
err = document.querySelector(
'#error');
frm.addEventListener('submit',
function(e) {
err.textContent =
'';
if (user.value.trim() ===
'') {
err.textContent =
'Please fill user name.';
return false;
}
if (pwd.value.trim() ===
'') {
err.textContent =
'Please use valid password.';
return false;
}
}); // end function
});
});
</script>
<script>
//Fading in Advertisent
$(document).ready(function() {
$("#ad").animate({
top: '100px',
}, (5000));
//Closing The Advertisement
$("#adbtn").click(function() {
$("#ad").fadeOut(5000);
});
$(".plus").click(function() {
$("form").slideToggle(1000); // half second duration
$(this).toggleClass("plus").toggleClass(
"minus");
var userName = document.getElementById(
"username").value;
var password = document.getElementById(
"pw").value;
//Error Variables_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
var milesDrivenError = document
.getElementById("error");
var gallonsUsedError = document
.getElementById("error");
//Clear out error messages eveerytime
milesDrivenError.firstChild.nodeValue =
"";
gallonsUsedError.firstChild.nodeValue =
"";
//**********************************************************
// Step 3: check for valid username
// if (not a number),
// write an error message to the form
// using the miles_driven_error id
//**********************************************************
if (isNaN(userName) || userName <=
0) {
milesDrivenError.firstChild
.nodeValue =
"Please Enter A Valid Username";
return false;
} //end if
//**********************************************************
// Step 4: check for valid gallons used
// if (not a number OR gallons used < 0),
// write an error message to the form
// using the gallons_used_error id
//**********************************************************
if (isNaN(password) || password <=
0) {
gallonsUsedError.firstChild
.nodeValue =
"Please Enter A Valid Password";
return false;
} //end if
function formSubmit() {
document.getElementById(
"form").submit();
document.getElementById(
"error").firstChild
.nodeValue = "";
}
//**********************************************************
// Step 9: define an anonymous function for window.onload
// This function should assign the event handler
// functions for the Calculate and Clear buttons
//**********************************************************
function init() {
document.getElementById(
"button").onclick =
formSubmit;
}
window.onload = init;
var frm = document.querySelector(
'form'),
user = document.querySelector(
'#username'),
pwd = document.querySelector(
'#pw'),
err = document.querySelector(
'#error');
frm.addEventListener('submit',
function(e) {
err.textContent =
'';
if (user.value.trim() ===
'') {
err.textContent =
'Please fill user name.';
return false;
}
if (pwd.value.trim() ===
'') {
err.textContent =
'Please use valid password.';
return false;
}
}); // end function
});
});
</script>
body {
background-color: #fff;
font-family: arial, sans-serif;
font-size: 100%;
}
a {
color: blue;
}
#welcome p strong {
color: navy;
font-size: 1.2em;
}
#welcome p:first-of-type {
margin-bottom: 50px;
}
section {
margin-bottom: 50px;
}
/* main container */
#main {
width: 960px;
margin: 50px auto;
border: 2px solid #000;
padding: 20px;
background-color: #e0e0ff;
position: relative;
box-sizing: border-box;
}
/* form container */
#loginDiv {
width: 300px;
position: absolute;
left: 650px;
top: 6px;
z-index: 100;
border: 1px solid navy;
}
/* paragraph that shows the text "Login" which is clicked on to display/remove the form */
#login {
margin: 0;
cursor: pointer;
background-color: rgb(255, 255, 255);
padding: 5px 0 2px 30px;
}
#login:hover {
background-color: rgb(110, 138, 195);
}
/* plus sign icon for login form */
.plus {
background: url(img_open.png) no-repeat 8px 7px;
background-color: rgb(110, 138, 195);
}
/* minus sign icon for login form */
.minus {
background: url(img_close.png) no-repeat 8px 7px;
}
/*form is hidden when the page loads */
#loginDiv form {
padding: 10px 10px 10px 10px;
display: none;
background-color: rgb(255, 255, 255);
}
#loginDiv label {
display: block;
width: 100px;
margin: 0 15px 0 0;
}
#loginDiv input {
font-size: 1.2em;
border: 1px solid navy;
}
#loginDiv input:focus {
background-color: rgb(110, 138, 195);
border: 2px solid navy;
}
#loginDiv input[type=button] {
width: 100px;
}
footer {
text-align: center;
margin-top: 50px;
margin-bottom: 10px;
padding: 20px;
border-top: 1px solid #000;
}
/* ad is not shown when the page loads */
#ad {
width: 300px;
height: 300px;
border: 1px solid #000;
background-color: yellow;
position: absolute;
left: 330px;
top: -500px;
/* you can change this inbitially for viewing purposes only but be sure to set it back */
box-sizing: border-box;
background-image: url(ad.jpg);
background-repeat: no-repeat;
}
/* close button on ad */
#adbtn {
width: 50px;
height: 50px;
border: 2px solid #000;
border-top-width: 1px;
border-right-width: 1px;
background-color: #fff;
font-size: 3em;
text-align: center;
cursor: pointer;
box-sizing: border-box;
position: absolute;
top: 0px;
right: 0px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script href="http//ajax.aspnetcdn.com/ajax/jquery.validate/1.15.0/jquery.validate.js"></script>
<!-- main container -->
<div id="main">
<section id="loginDiv">
<!-- when this is clicked on the below form should be displayed and plus sign should change to minus sign-->
<p id="login" class="plus">Login</p>
<form>
<p>
<label for="username">Username:</label>
<input type="text" name="username" id="username">
</p>
<p>
<label for="pw">Password:</label>
<input type="password" name="pw" id="pw">
</p>
<p>
<input type="button" value="Submit">
</p>
<!-- placeholder for response if form data is correct/incorrect -->
<p id="error"></p>
</form>
</section>
<section id="welcome">
<h1>Welcome to the Local jQuery User Group Website</h1>
<p> <strong>Click the login button at the top of the page to login. To become a member please <a href="#">Register</a></strong>
</p>
<h2>About this page layout:</h2>
<p>The main container (parent) has 'relative' positioning so that the 'login' container can be absolutley positioned with respect to that main container. Otherwise, it would default to being absolutley positioned with respect to the window.</p>
<p>In order for the login panel to be placed on top of the page we need to use absolute positioning, otherwise, it would move the rest of the content down as done in the FAQ assignment. Technically, absolute positioning takes that element out of the
normal flow of the document, so that it is on top of the page. The 'ad' is also absolutely positioned to the same main container.</p>
</section>
<section>
<h2>This week's agenda:</h2>
<p>There will be a live meeting this Tuesday evening from 7:00pm to 8:00pm PST using our WebEx Conferencing Software. It will be recorded! Please note that the code samples will be available on our GitHub repository.</p>
</section>
<footer>Copyright © Local jQuery User Group</footer>
<!-- ad which is absolutely positioned -500px from the top so you do not see it when page loads-->
<div id="ad">
<div id="adbtn">X</div>
</div>
<!-- end main container -->
</div>
推荐答案
我尝试了jquery，但是我想学习JavaScript方式.
好吧！
使用表单时，如果要验证表单，则最好使用submit事件与input[type="submit"]按钮一起使用.
When you're working with form and you want to validate the form then form submit event should be better choice to use with input[type="submit"] button.
var frm = document.querySelector('form'),
user = document.querySelector('#username'),
pwd = document.querySelector('#pw'),
err = document.querySelector('#error');
frm.addEventListener('submit', function(e) {
err.textContent = '';
if (user.value.trim() === '') {
err.textContent = 'Please fill user name.';
return false;
}
if (pwd.value.trim() === '') {
err.textContent = 'Please use valid password.';
return false;
}
});
<form action='#' method='post'>
<p>
<label for="username">Username:</label>
<input type="text" name="username" id="username">
</p>
<p>
<label for="pw">Password:</label>
<input type="password" name="pw" id="pw">
</p>
<p>
<input type="submit" value="Submit">
</p>
<!-- placeholder for response if form data is correct/incorrect -->
<p id="error"></p>
</form>
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