如何防止表单被提交？

Question

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.

Answer 1

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...

html

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

function mySubmitFunction(e) {
  e.preventDefault();
  someBug();
  return false;
}

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

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

function mySubmit(e) { 
  e.preventDefault(); 
  try {
   someBug();
  } catch (e) {
   throw new Error(e.message);
  }
  return false;
}

Answer 2

You can use inline event onsubmit like this

<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.

Answer 3

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

 const element = document.querySelector('form'); element.addEventListener('submit', event => { event.preventDefault(); // actual logic, eg 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 .

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 .

Answer 4

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 eg e.preventDefault()

Answer 5

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.");
    });
});

Answer 6

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

Answer 7

For prevent form from submittion you only need to do this.

<form onsubmit="event.preventDefault()">
    .....
</form>

By using above code this will prevent your form submittion.

Answer 8

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.

Answer 9

You can add eventListner to the form, that preventDefault() and convert form data to JSON as below:

 const formToJSON = elements => [].reduce.call(elements, (data, element) => { data[element.name] = element.value; return data; }, {}); const handleFormSubmit = event => { event.preventDefault(); const data = formToJSON(form.elements); console.log(data); // const odata = JSON.stringify(data, null, " "); const jdata = JSON.stringify(data); console.log(jdata); (async () => { const rawResponse = await fetch('/', { method: 'POST', headers: { 'Accept': 'application/json', 'Content-Type': 'application/json' }, body: jdata }); const content = await rawResponse.json(); console.log(content); })(); }; const form = document.forms['myForm']; form.addEventListener('submit', handleFormSubmit);

 <form id="myForm" action="/" method="post" accept-charset="utf-8"> <label>Checkbox: <input type="checkbox" name="checkbox" value="on"> </label><br /><br /> <label>Number: <input name="number" type="number" value="123" /> </label><br /><br /> <label>Password: <input name="password" type="password" /> </label> <br /><br /> <label for="radio">Type: <label for="a">A <input type="radio" name="radio" id="a" value="a" /> </label> <label for="b">B <input type="radio" name="radio" id="b" value="b" checked /> </label> <label for="c">C <input type="radio" name="radio" id="c" value="c" /> </label> </label> <br /><br /> <label>Textarea: <textarea name="text_area" rows="10" cols="50">Write something here.</textarea> </label> <br /><br /> <label>Select: <select name="select"> <option value="a">Value A</option> <option value="b" selected>Value B</option> <option value="c">Value C</option> </select> </label> <br /><br /> <label>Submit: <input type="submit" value="Login"> </label> <br /><br /> </form>

Answer 10

<form v-on:submit.prevent="yourMethodHere">

The submit event will no longer reload the page. It runs your method.

From vue documentation: https://vuejs.org/guide/essentials/event-handling.html#event-modifiers

Answer 11

Here my answer :

<form onsubmit="event.preventDefault();searchOrder(event);">
...
</form>
<script>
const searchOrder = e => {
    e.preventDefault();
    const name = e.target.name.value;
    renderSearching();

    return false;
}
</script>

I add event.preventDefault(); on onsubmit and it works.