Develop Reference

Placeholder only appears for split second [duplicate]

I'm working on an ASP.net web application.
I have a form with a submit button. The code for the submit button looks like <input type='submit' value='submit request' onclick='btnClick();'>.
I want to write something like the following:
function btnClick() {
if (!validData())
cancelFormSubmission();
}
How do I do this?

You are better off doing...
<form onsubmit="return isValidForm()" />
If isValidForm() returns false, then your form doesn't submit.
You should also probably move your event handler from inline.
document.getElementById('my-form').onsubmit = function() {
return isValidForm();
};

Change your input to this:
<input type='submit' value='submit request' onclick='return btnClick();'>
And return false in your function
function btnClick() {
if (!validData())
return false;
}

You need to change
onclick='btnClick();'
to
onclick='return btnClick();'
and
cancelFormSubmission();
to
return false;
That said, I'd try to avoid the intrinsic event attributes in favour of unobtrusive JS with a library (such as YUI or jQuery) that has a good event handling API and tie into the event that really matters (i.e. the form's submit event instead of the button's click event).

Sometimes onsubmit wouldn't work with asp.net.
I solved it with very easy way.
if we have such a form
<form method="post" name="setting-form" >
<input type="text" id="UserName" name="UserName" value=""
placeholder="user name" >
<input type="password" id="Password" name="password" value="" placeholder="password" >
<div id="remember" class="checkbox">
<label>remember me</label>
<asp:CheckBox ID="RememberMe" runat="server" />
</div>
<input type="submit" value="login" id="login-btn"/>
</form>
You can now catch get that event before the form postback and stop it from postback and do all the ajax you want using this jquery.
$(document).ready(function () {
$("#login-btn").click(function (event) {
event.preventDefault();
alert("do what ever you want");
});
});

you should change the type from submit to button:
<input type='button' value='submit request'>
instead of
<input type='submit' value='submit request'>
you then get the name of your button in javascript and associate whatever action you want to it
var btn = document.forms["frm_name"].elements["btn_name"];
btn.onclick = function(){...};
worked for me
hope it helps.

This is a very old thread but it is sure to be noticed. Hence the note that the solutions offered are no longer up to date and that modern Javascript is much better.
<script>
document.getElementById(id of the form).addEventListener(
"submit",
function(event)
{
if(validData() === false)
{
event.preventDefault();
}
},
false
);
The form receives an event handler that monitors the submit. If the there called function validData (not shown here) returns a FALSE, calling the method PreventDefault, which suppresses the submit of the form and the browser returns to the input. Otherwise the form will be sent as usual.
P.S. This also works with the attribute onsubmit. Then the anonymus function function(event){...} must in the attribute onsubmit of the form. This is not really modern and you can only work with one event handler for submit. But you don't have to create an extra javascript. In addition, it can be specified directly in the source code as an attribute of the form and there is no need to wait until the form is integrated in the DOM.

You need to return false;:
<input type='submit' value='submit request' onclick='return btnClick();' />
function btnClick() {
return validData();
}

With JQuery is even more simple: works in Asp.Net MVC and Asp.Core
<script>
$('#btnSubmit').on('click', function () {
if (ValidData) {
return true; //submit the form
}
else {
return false; //cancel the submit
}
});
</script>

Why not change the submit button to a regular button, and on the click event, submit your form if it passes your validation tests?
e.g
<input type='button' value='submit request' onclick='btnClick();'>
function btnClick() {
if (validData())
document.myform.submit();
}

You need onSubmit. Not onClick otherwise someone can just press enter and it will bypass your validation. As for canceling. you need to return false. Here's the code:
<form onSubmit="return btnClick()">
<input type='submit' value='submit request'>
function btnClick() {
if (!validData()) return false;
}
Edit onSubmit belongs in the form tag.

It's simple, just return false;
The below code goes within the onclick of the submit button using jquery..
if(conditionsNotmet)
{
return false;
}

use onclick='return btnClick();'
and
function btnClick() {
return validData();
}

function btnClick() {
return validData();
}

<input type='button' onclick='buttonClick()' />
<script>
function buttonClick(){
//Validate Here
document.getElementsByTagName('form')[0].submit();
}
</script>

returning false not stopping the submission of form

My purpose: If the user field and password field are blank, I want to stop form submitting.
This is my Code that I am trying:
<!DOCTYPE html>
<html>
<head>
<script>
function doit() {
var usr = document.getElementById('ur').value;
var psw = document.getElementById('pw').value;
if ((usr.trim() == '') && (psw.trim() == '')) {
alert("cannot Submit form");
return false;
}
}
</script>
</head>
<body>
<form action="post.php" method="post" onsubmit="doit()">
User:
<input type="text" id="ur" name="user">
<br>
<br> Pass:
<input type="password" id="pw" name="pass">
<br>
<br>
<button>Submit</button>
</form>
</body>
</html>
I am learning JavaScript. Will be helpful if you correct the code with a little explanation why it is not working.

return false is working fine, the way you are calling that function is wrong.
<form action="post.php" method="post" onsubmit="doit()">
Just calls it, doesn't do anything with the return value
<form action="post.php" method="post" onsubmit="return doit()">
^
Will stop the form post on a false returned value.
Read this note on MSDN although it is not IE specific
You can override this event by returning false in the event handler. Use this capability to validate data on the client side to prevent invalid data from being submitted to the server. If the event handler is called by the onsubmit attribute of the form object, the code must explicitly request the return value using the return function, and the event handler must provide an explicit return value for each possible code path in the event handler function.
Now onto another important point.
Your if condition will only stop form submission when both the fields are blank, whereas it should do that even if any one of those two fields is blank. That && (AND) should be an || (OR), and at the end of your functions if nothing returned false, return true then.

onsubmit event accepts boolean values, since you are not returning anything so it assumes true by default. You need to add return in this event explicitly like mentioned below:
change
onsubmit="doit()">
to
onsubmit="return doit()">

Using addEventListener on submit with preventDefault()
document.form1.addEventListener( "submit", function(event) {
var user = this.querySelector("input[name=user]").value; // this = object of form1
var pass = this.querySelector("input[name=pass]").value;
if ( (user.trim() == "") || (pass.trim() == "") ) {
alert("cannot Submit form");
event.preventDefault();
} else {
alert("submit");
}
} );
<form action="" method="post" name="form1" >
Username: <input type="text" name="user" /><br><br>
Password: <input type="password" name="pass" /><br><hr>
<input type="submit" value="Submit" />
</form>
codepen
repl.it

Preventing form submission after validation by parsley.js

I have used parsley.js many times and have literally copied the code from my last use of parsley.
However, every time I submit the form the page refreshes. preventDefault seems to work on my other pages and stops the page from refreshing but for some reason when I tried now it won't work. Can anyone figure out why not?
<script>
$(function(){
$("#register_signup").submit(function(e){
e.preventDefault();
var form = $(this);
if ($('#rform').parsley( 'isValid' )){
alert('valid');
}
});
});
</script>
<form id='rform' name='rform' data-parsley-validate>
<input id='reg_password' class='register_input' type='text' autocomplete="off" data-parsley-trigger="change" placeholder='Password' required>
<input id='reg_cpassword' class='register_input' type='text' name="reg_cpassword" placeholder='Confirm password' data-parsley-equalto="#reg_password" required>
<input id='register_signup' type="submit" onClick="javascript:$('#rform').parsley( 'validate' );" value='Sign Up' />
</form>

You are binding the submit event to a input element. If you check the jquery $.submit() documentation, it states that:
The submit event is sent to an element when the user is attempting to submit a form. It can only be attached to <form> elements. Forms can be submitted either by clicking an explicit <input type="submit">, <input type="image">, or <button type="submit">, or by pressing Enter when certain form elements have focus.
This is your main problem and this is why alert will never be displayed (in fact, that code is never executed).
I would also change a few things:
$('#rform').parsley( 'validate' ) should be $('#rform').parsley().validate(), assuming you are using Parsley 2.*
$('#rform').parsley( 'isValid' ) should be $('#rform').parsley().isValid().
Use $.on() instead of $.submit().
Remove onClickfrom the register_signup element. Since you are already using javascript, I would do this directly in the javascript code instead of onclick. This is more a personal preference.
So, your code will be something like this:
<form id='rform' name='rform'>
<input id='reg_password' class='register_input' type='text' autocomplete="off"
data-parsley-trigger="change" placeholder='Password' required>
<input id='reg_cpassword' class='register_input' type='text' name="reg_cpassword"
placeholder='Confirm password' data-parsley-equalto="#reg_password" required>
<input id='register_signup' type="submit" value='Sign Up' />
</form>
<script>
$(document).ready(function() {
$("#rform").on('submit', function(e){
e.preventDefault();
var form = $(this);
form.parsley().validate();
if (form.parsley().isValid()){
alert('valid');
}
});
});
</script>

if you are using parsely 2 you can try this
$(function () {
//parsely event to validate form -> form:valiate
$('#rform').parsley().on('form:validate', function (formInstance) {
//whenValid return promise if success enter then function if failed enter catch
var ok = formInstance.whenValid()
//on success validation
.then(function(){
alert('v');
formInstance.reset();
})
//on failure validation
.catch(function(){
formInstance.destroy();
});
$('.invalid-form-error-message')
.html(ok ? '' : 'You must correctly fill *at least one of these two blocks!')
.toggleClass('filled', !ok);
// console.log(formInstance);
if (!ok)
formInstance.validationResult = false;
console.log(formInstance);
});
//parsely event to submit form -> form:submit
$('#rform').parsley().on('form:submit', function (formInstance) {
// if you want to prevent submit in any condition after validation success -> return it false
return false;
});
//default submit still implemented but replaced with event form:submit
$('#rform').submit(function () {
alert('dd');
});
});
for more details parsely documentation check Form with examples and events

When you apply data-parsley-validate to your form, you don't need to apply javascript to form to stop submit until all validation run.
But if you applying javascript return false when parsely() not valid.
And just make sure you have include parsley.js code file.

How to create html5 custom validation?

I am using html 5 form validation for validate my form before submit, if is valid, submit, but I need validate my User Register form, so it need validate if Password Confirm value is equal camp Password, below is my form example:
<form>
<label>Login:</label>
<input type="text" name="login" id="login"/><br/>
<label>Password:</label>
<input type="password" name="pass" id="pass"/><br/>
<label>Password Confirm:</label>
<input type="password" name="pass_conf" id="pass_conf"/><br/>
<input type="submit"/>
</form>
or in jsfiddle
How to can I create my custom validation for work like default validations?

Well you can use JQuery and attach an attribute to be selected for the passwords to validate each other via input event. Use setCustomValidity() to set the message of the input affected to override the default message when the form is submitted.
See the updated fiddle.
As you can see in the fiddle, all you have to do is add an attribute data-equal-id wherein the attribute value must be the ID of password input element to be tested.
HTML
<h1>How to create html5 validation for password confirm?</h1>
<hr>
<form>
<label>Login:</label>
<input type="text" name="login" id="login"/><br/>
<label>Password:</label>
<input type="password" name="pass" id="pass"/><br/>
<label>Password Confirm:</label>
<input type="password" name="pass_conf" id="pass_conf" data-equal-id="pass" /><br/>
<input type="submit"/>
</form>
Javascript
$('[data-equal-id]').bind('input', function() {
var to_confirm = $(this);
var to_equal = $('#' + to_confirm.data('equalId'));
if(to_confirm.val() != to_equal.val())
this.setCustomValidity('Password must be equal');
else
this.setCustomValidity('');
});

you could try putting this code in your header:
<script>
document.getElementById('myform').onsubmit = function() {
if(!validateForm()){ // call your validation function
alert('fail!'); // remove this
return false; // prevent the form to submit
}
}
// your validation function
// compares that the passwords are equal
function validateForm(){
var pass = document.getElementById('pass').value;
var pass_conf = document.getElementById('pass_conf').value;
if(pass == pass_conf){
return true;
}else{
return false;
}
}
</script>
also put the id 'myform' to your form (or the name you want, but change it in the first line)

How about something fun like this using jQuery?
$('input[type="password"]').keyup(function() {
var pass=$('#pass').val();
var conf=$('#pass_conf').val();
if (pass == conf)
$('input[type="submit"]').removeAttr('disabled');
else
$('input[type="submit"]').attr('disabled', 'disabled');
});
The breakdown...
I am keying off of the keyup, so every time a key is pressed in the
password fields the function will fire.
I'm grabbing the value of both password fields, and comparing them.
If the values are the same, I'm enabling the submit button.
If the values are different, I'm disabling the submit button.
Pretty simple, but it works. Here is a demo: http://codepen.io/anon/pen/GxAyC/
(note - I added a couple of other visual enhancements to the demo to show what can be done)

You're using HTML5 for client-side form validation and wish to validate your form prior to form submission. Your form consists of three inputs and your only validation criteria is that both password fields match.
The most simple way to do this is to write a custom submit handler script:
const handleFormSubmit = (event) => {
event.preventDefault();
form = event.target;
if (form.pass === form.pass_conf) {
form.submit();
}
}
Above preventDefault() stops the default form submission behavior so you can execute your check. Then check if the value of the two password fields are equal. And if they are, continue form submission.
To use, attach the custom handler to your form by listening to the submit event:
const form = document.querySelector('form');
form.addEventListener('submit', handleFormSubmit);
Applied in context to example form provided:
<form>
<label>Login:</label>
<input type="text" name="login" id="login"/><br/>
<label>Password:</label>
<input type="password" name="pass" id="pass"/><br/>
<label>Password Confirm:</label>
<input type="password" name="pass_conf" id="pass_conf"/><br/>
<input type="submit"/>
</form>
<script>
const form = document.querySelector('form');
form.addEventListener('submit', handleFormSubmit);
const handleFormSubmit = (event) => {
event.preventDefault();
form = event.target;
if (form.pass.value === form.pass_conf.value) {
form.submit();
}
}
</script>

Preventing from form submission when validation fails

How do I prevent this from submission when validation fails? I don't know what to put in the validateForm function... I have this form:
<form action="ChangePassword" method="POST">
<input type="submit" value="Change Password" onclick="validateForm();"/>
</form>
And the validateform function:
<script>
function validateForm() {
if(document.getElementById("passError").innerHTML !== "") {
alert("There are some errors.");
return false;
}
}
</script>

You need to return from your event handler function.
You are currently only returning from validateForm which is a function you call from your event handler function.
onclick="return validateForm();"
Good practise would be:
to perform the check when it is submitted rather then only when the submit button is clicked (i.e. use onsubmit on the form instead of onclick on the button).
to bind your event handlers with JavaScript instead of depending on globals and intrinsic event attributes

Maybe you have to stop the bubbling from your scope with e.preventDefault() instead of return false ?
function validateForm(event) {
if(document.getElementById("passError").innerHTML !== "") {
alert("There are some errors.");
event.preventDefault();
}
}

You have to do it in your form. Not in submit button. Like:
<form name="myForm" onsubmit="return validateForm();">
And also return true if your validation passes in your validate function.