Develop Reference

How to validate an html5 form and show error tips on a button click?

I have a button submit inside a form and just a normal button outside of it. I want to validate a form:
function myButtonHandler(evt) {
if (myForm.checkValidity()) {
alert("yes");
} else {
alert("no");
}
}
This doesn't show the standard error tips inside of input elements when they're invalid when I click on a button -- ones shown by a browser when I click the submit button. How can I get these validation message to pop up when I click on my normal button when the form is invalid?
<form id="my_form">
<input type="text" placeholder="Name" required="true"/>
<input type="submit" id="submit" value="go" />
</form>
No jquery.

You'll need to add the code you've shown to a function that is set up as the click event callback for the normal button:
var myForm = document.querySelector("form"); // reference to form
var btn = document.querySelector("[type='button']"); // reference to normal button
// Set up click event handling function for normal button
btn.addEventListener("click", function(){
if (myForm.checkValidity()) {
alert("yes");
} else {
alert("no");
}
});
<form>
<input type="text" required>
<button type="submit">submit</button>
</form>
<button type="button">Check Validity</button>
If you just want to show the normal browser's validation errors, you can make the second button also a submit button. It's OK for the button to be outside of the form as long as you tie it back to the form with the form attribute.
<form id="theForm">
<input type="text" required>
<button type="submit">submit</button>
</form>
<button type="submit" form="theForm">Check Validity</button>

empty check for multiple form in a page separately

I have two forms (consist with input,textarea,checkbox) in a page. I want check emptiness of these forms separately on click seperate button.
I use the following script. But it shows empty message if any of these form input is empty.
$('#submit').click(function(e) {
var empty = false;
$('input, textarea').each(function() {
if ($(this).val() == '') {
empty = true;
}
});
if (empty) {
alert("empty");
e.preventDefault();
}
else {
document.getElementById("contact").submit();
}
})()

Never assign stuff to submit buttons
Do not submit a form from a submit button if you have chosen to use preventDefault if something wrong. It could submit the form twice
$(function() {
// on the submit event NOT the button click
$('form').on("submit", function(e) { // any form - use .formClass if necessary to specific forms
var empty = false;
$("input, textarea", this).each(function() { // this form's inputs incl submit
if ($.trim($(this).val()) == "") { // trim it too
console.log(this.name,"empty")
empty = true;
return false; // no need to continue
}
});
if (empty) {
alert(this.id + " is empty"); // or set a class on the div
e.preventDefault(); // cancel submission
}
});
});
div {
border: 1px solid black;
width:500px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<form id="form1">
<div>
<input type="text" value="" name="field1" /><br/>
<textarea name="field2"></textarea><br/>
<input type="submit" value="Submit" />
</div>
</form>
<hr/>
<form id="form2">
<div>
<input type="text" value="" name="field3" /><br/>
<textarea name="field4"></textarea><br/>
<input type="submit" value="Submit" />
</div>
</form>
You could also add required to the fields

You need to restrain the handler to the form containing the clicked button:
$('#submit').click(function(e) {
var form = $(this).parents('form:first');
var empty = false;
$('input, textarea', form).each(function() {
// the rest is the same
I'd also like to point out that you cannot have the same ID on multiple controls, so
$('#submit')
should always return exactly one button. You should do something like this, where you distinguish the buttons by class instead:
<input type="submit" id="submitA" class="submitButton">
<input type="submit" id="submitB" class="submitButton">
and select with
$('.submitButton')

you know you can also use jquery to reset the form like so
form.resetForm();

PHP form submit button but not leave page

I have a button that links to a php file that tracks user's email when clicked, but I don't want the user to leave the page when button is clicked, I just want to change button's value.
This is the html of the form.
<form action="mysql-query.php" method="post">
<input type="text" name="email" style="display:none;">
<input type="submit" value="Press here" id="test" onclick="Press()">
</form>
And this is the script that handles the form:
<script>
function Press() {
var test= document.getElementById("test");
test.value="Thank you";
localStorage.value=("ok");
}
</script>
I put the display:none; because I don't want to display anything but the button and have a way to connect with my php file.
Any ideas?

You need to use ajax:
html:
<form action="mysql-query.php" method="post" onsubmit="return Press(this)">
<input type="text" name="email" style="display:none;">
<input type="submit" value="Press here" id="test">
</form>
js:
function Press(form) {
$.post($(form).attr('action'), function() {
var test= document.getElementById("test");
test.value="Thank you";
localStorage.value=("ok");
});
return false; // prevent submitting the form
}
or better bind submit event using jQuery:
$('form').submit(function() {
$.post($(this).attr('action'), function() {
var test= document.getElementById("test");
test.value="Thank you";
localStorage.value=("ok");
});
return false; // prevent submitting the form
});

Use:
<form action="javascript:void()">
Ok, this thing prevents the form from sending the data anywhere, unless you use "onclick" event on the submit button.

What you can do is remove the type="submit" on the button and replace it with type="button". Next you can do an ajax call to your php and do your magic.

posting form by jquery not working

Basically i have submitted the form data by using jquery event in order to prevent page reload. Now , the informations of the form are not being displayed?
$("#btn-ser1").click(function() {
$("#form").submit(function() {
alert("you are submitting" + $(this).serialize());
});
});
<html>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<body>
<form method="post" id="form">
First Name :
<input name="fname">Last Name :
<input name="lname">Address :
<input name="address">Contact No. :
<input name="contact">Country:
<input name="country">City:
<input name="city">
</form>
<button type="button" id="btn-ser1">Serialize</button>
</body>
</html>

You aren't submitting, neither preventing the default action. You need:
$("#btn-ser1").click(function () {
// remove this event handler « #1
// $("#form").submit(function (e) {
// prevent refresh or default action « #2
e.preventDefault();
// change $(this) to $("#form") as you are binding it to the button, not the form.
alert("you are submitting" + $("#form").serialize());
// submit to the server « #3
$.post("path/to/post", $("#form").serialize());
// });
});
You forgot to do the #1, #2 and #3 as mentioned.

Your button is the incorrect type. This only works with a "Submit" button. Use this HTML snippet instead:
<button type="submit" id="btn-ser1">Serialize</button>

my jquery form validation is not working as i hope it should

I have some javascipt code here that validates a user form. When the user inputs the correct answer it tells them and gives them the link to the next question. At least, that's what it is supposed to do. When i click the form it reloads the page but it should not because i added return false.
the div tra holds 35
and the div usermsg is the user inputted value.
<script>
$("#submit").click(function(){
var clientmsg6 = $("#usermsg").val();
var rightanswer = $("#tra").val();
if (clientmsg6<>rightanswer)
{
$("#confirm").html("<h2>Sorry, wrong answer.</h2>");
}
else
{
$("#confirm").html("<a href='#' onclick='play();' style='font-size:20px;' id='new1'>Click here for Question 2</a>");
}
return false;
});
</script>
Any ideas why this is not working?

It should be
if (clientmsg6 != rightanswer)
not
if (clientmsg6<>rightanswer)

To prevent a form submission, you need to return false on the form itself instead of on the submit button. Your code should become:
HTML
<form action="page.php" method="post">
<input id="usermsg" type="text" name="answer" />
<input id="submit" type="submit" value="Submit" />
</form>
JS (please note the line where you have clientmsg6, you have a syntax error)
$("#myform").on('submit', function(){
var clientmsg6 = $("#usermsg").val();
var rightanswer = $("#tra").val();
if (clientmsg6 != rightanswer) { //This line was also wrong, should be != instead of <>
$("#confirm").html("<h2>Sorry, wrong answer.</h2>");
}
else {
$("#confirm").html("<a href='#' onclick='play();' style='font-size:20px;' id='new1'>Click here for Question 2</a>");
}
return false;
});
Alternatively, you can keep your existing code by changing your submit button to be just a plain old button, but you will lose the extra functionality of the user being able to hit the enter key and performing the same action.
<form action="page.php" method="post">
<input id="usermsg" type="text" name="answer" />
<input id="submit" type="button" value="Submit" />
</form>

Instead of using .html(), try using .text()

if #submit is a link tag otherwise use the form ID and the submit event
$("#submit").click(function(e){
e.preventDefault()
...
...
...
});

You need to attach handlers once the document has finished loading.
Wrap your script in the following
<script>
$(function() {
// script
});
</script>