Clash Royale CLAN TAG#URR8PPP

How to prevent form from being submitted?

I have a form that has a submit button in it somewhere.

However, I would like to somehow 'catch' the submit event and prevent it from occurring.

Is there some way I can do this?

I can't modify the submit button, because it's part of a custom control.

7 Answers
7

Unlike the other answers, return false is only part of the answer. Consider the scenario in which a JS error occurs prior to the return statement...

false

html

<form onsubmit="return mySubmitFunction(evt)">
...
</form>


script

function mySubmitFunction()

someBug()
return false;



returning false here won't be executed and the form will be submitted either way. You should also call preventDefault to prevent the default form action for Ajax form submissions.

false

preventDefault

function mySubmitFunction(evt)
evt.preventDefault();
someBug();
return false;



In this case, even with the bug the form won't submit!

Alternatively, a try...catch block could be used.

try...catch

function mySubmit(evt)
evt.preventDefault();
try
someBug();
catch (e)
throw new Error(e.message);

return false;



false

onsumbit

(<form onsubmit="return mySubmitFunction(evt)">)

You can use inline event onSubmit like this

onSubmit

<form onsubmit="alert('stop submit'); return false;" >


Or

<script>
function toSubmit()
alert('I will not submit');
return false;

</script>

<form onsubmit="return toSubmit();" >


Demo

Now, this may be not a good idea when making big projects. You may need to use Event Listeners.

Please read more about Inline Events vs Event Listeners (addEventListener and IE's attachEvent) here. For I can not explain it more than Chris Baker did.

Both are correct, but none of them are "best" per se, and there may be
a reason the developer chose to use both approaches.

Attach an event listener to the form using .addEventListener() and then call the .preventDefault() method on event:

.addEventListener()

.preventDefault()

event

const element = document.querySelector('form');
element.addEventListener('submit', event =>
event.preventDefault();
// actual logic, e.g. validate the form
console.log('Form submission cancelled.');
);

<form>
<button type="submit">Submit</button>
</form>

I think it's a better solution than defining a submit event handler inline with the onsubmit attribute because it separates webpage logic and structure. It's much easier to maintain a project where logic is separated from HTML. See: Unobtrusive JavaScript.

submit

onsubmit

Using the .onsubmit property of the form DOM object is not a good idea because it prevents you from attaching multiple submit callbacks to one element. See addEventListener vs onclick
.

.onsubmit

form

$("button").click(function(e) e.preventDefault() );

Try this one...

HTML Code

<form class="submit">
<input type="text" name="text1"/>
<input type="text" name="text2"/>
<input type="submit" name="Submit" value="submit"/>
</form>


jQuery Code

$(function()
$('.submit').on('submit', function(event)
event.preventDefault();
alert("Form Submission stopped.");
);
);


or

$(function()
$('.submit').on('submit', function(event)
event.preventDefault();
event.stopPropagation();
alert("Form Submission prevented / stopped.");
);
);


var form = document.getElementById("idOfForm");
form.onsubmit = function()
return false;



.onsubmit

submit

.addEventListener()

The following works as of now (tested in chrome and firefox):

<form onsubmit="event.preventDefault(); return validateMyForm();">


where validateMyForm() is a function that returns false if validation fails. The key point is to use the name event. We cannot use for e.g. e.preventDefault()

false

event

e.preventDefault()

To follow unobtrusive JavaScript programming conventions, and depending on how quickly the DOM will load, it may be a good idea to use the following:

<form onsubmit="return false;"></form>


Then wire up events using the onload or DOM ready if you're using a library.

$(function()
var $form = $('#my-form');
$form.removeAttr('onsubmit');
$form.submit(function(ev)
// quick validation example...
$form.children('input[type="text"]').each(function()
if($(this).val().length == 0)
alert('You are missing a field');
ev.preventDefault();

);
);
);

label
display: block;


#my-form > input[type="text"]
background: cyan;


<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form id="my-form" action="http://google.com" method="GET" onsubmit="return false;">
<label>Your first name</label>
<input type="text" name="first-name"/>
<label>Your last name</label>
<input type="text" name="last-name" /> <br />
<input type="submit" />
</form>

Also, I would always use the action attribute as some people may have some plugin like NoScript running which would then break the validation. If you're using the action attribute, at the very least your user will get redirected by the server based on the backend validation. If you're using something like window.location, on the other hand, things will be bad.

action

window.location

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