jQuery using event.preventDefault() with on('input')

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I'm catching paste events with $('selector').on('input', function(event) { ... });

Then I'm trying to test what's been pasted and if it doesn't pass validation, cancel the paste with event.preventDefault(). Unfortunately, by the time the listener function is executed, the text has already been pasted and event.preventDefault() does nothing.

So what's a good way to catch paste events, and if what's been pasted doesn't validate, undo/prevent the paste?

I know I can use .on('paste', function(event) { ... }), but that doesn't give me the text that's been pasted or the contents of the input element after the paste, unless I use setTimeout() with some minute wait time, and I'd like to avoid using setTimeout().

jQuery event.preventDefault() Method, Prevent a submit button from submitting a form; Prevent a link from following the URL. Tip: Use the event.isDefaultPrevented() method to check whether the  event.preventDefault() Returns: undefined Description: If this method is called, the default action of the event will not be triggered. version added: 1.0 event.preventDefault()

Try using .change event of jquery.

Set value to blank if value doesn't satisfy your condition.

jQuery, The preventDefault() Method in jQuery is used to stop the default action of selected element to occur. It is also used to Script to use event.preventDefault()​  Instead of using event.preventDefault(), we can capture the value when user input any content, using on('input')listener and validate it against the specific condition and if the validation gets failed, empty the text box value. (This is the workaround if we still need to use on('input')event listener)

Using

$('selector').on('input', function(event) { ... }); 

and in case the validation does not pass deleting the pasted text seems to work for me.

Sadly accessing the clipboard has some flaws (browser asking if it is allowed to inspect the clipboard, cross browser compatibility, etc.)

If you are okay with saving the last value of the input, the pasted text can be calculated anyway.

Here is my approach for calculating the pasted text

https://jsfiddle.net/f710o9qd/2/

I hope this helps you :)

(Feel free to refine the calculation of the pasted text if you find any flaws)

What e.preventDefault() method really does in jQuery?, The preventDefault() method stops the default action of a selected element from happening by a user. This method does not accept any  Description. The preventDefault() method prevents the browser from executing the default action.. You can use the method isDefaultPrevented to know whether this method was ever called (on that event object).

My understanding from the question is, we must not allow any data to be pasted inside the text box until and unless it pass a specific validation. Instead of using event.preventDefault(), we can capture the value when user input any content, using on('input') listener and validate it against the specific condition and if the validation gets failed, empty the text box value.

(This is the workaround if we still need to use on('input') event listener)

Sample Code (I am using console.log() for printing the pasted value):

HTML:

<input type='text' id="selector" />

JS:

$(document).ready(function() {
 $('#selector').on('input', function (e){
        if(e.target.value !== "myValue"){
        $('#selector').val('');
    }
    else{
        console.log(e.target.value);
    }
 });
});

jquery .click() event.preventDefault() not working, Since your links are appended dynamically to the page, you need to use document.on() to capture the click events. the syntax for appending  Thats because the click event generated by jQuery is just layer on top of native browser events. So triggering a 'click' event on an anchor tag wont follow the link. Instead you could use a library like jquery-simulate that will allow you to launch native browser events. More details about this can be found in this link

How to correctly use preventDefault(), stopPropagation(), or return , Despite this we still find ourselves going through code bases and event.​preventDefault(). Prevents the browsers default behaviour …in the context of jQuery, returning false will immediately exit the event listeners callback. Using preventDefault on a submit button. Ask Question I am trying to solve a problem offered by a jQuery textbook. event into the function in order to use

Event.preventDefault(), The Event interface's preventDefault() method tells the user agent Nowadays, you should usually use native HTML form validation instead. Actually any type of event, you can stop its default behavior with the preventDefault();So not only submit buttons, but keypresses, scrolling events, you name it and you can prevent it from happening. Or if you'd like add your own logic to the default behavior, think of logging an event or anything of your choice.

What is event.PreventDefault in jQuery?, The preventDefault() method tells the browser that if there is a default behaviour for this event on this object, then skip that default behaviour. This is not a jQuery  This means we will prevent our form from submitting using event.preventDefault and then we will do some validation logic and if we are happy, set allowSubmit to true. This is really the only effective method of doing the opposite of event.preventDefault () – you can also try removing events as well which essentially would achieve the same thing.

Comments
  • Can you create a jsFiddle example?
  • event.preventDefault() prevents the default action, and when binding to the input event, it does'nt really prevent you from typing or pasting anything in an input? When caching the value from pasted content, you'll have to defer it to get a value, but not "some minute", set the timeout to zero, and it should still work.
  • I guess it's ok if to set 100ms timeout to capture the value of a input on paste and validate rather than a minute.
  • You'd just do something like this FIDDLE ?
  • @adeneo The reason I'm averse to using setTimeout is because, as I understand, OS process scheduler may decide to give priorities to processes in such a way that the setTimeout function may be executed before the input element is updated with the pasted content. Though, I realize I may be completely wrong on this...
  • even though the event order is correct the 'change' will only bubble when the input looses its focus (immediately before blur). Also notice preventDefault won't stop the event chain - if you mean the event bubbling by it. If you want to achieve this you also need to call stopPropagation. (see w3schools.com/jsref/event_preventdefault.asp )
  • change-event will bubble very late (only after the input looses its focus)
  • The fiddle also applies the validation when some text is written rather than pasted. I hope this is what you intended.