[javascript] How do I cancel form submission in submit button onclick event?

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?

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 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.

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.

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.

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>

<input type='button' onclick='buttonClick()' />

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

You need to return false;:

<input type='submit' value='submit request' onclick='return btnClick();' />

function btnClick() {
    return validData();
}

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();
}

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 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).

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();
} 

function btnClick() {
    return validData();
}