问题
Once I\'ve fired an evt.preventDefault(), how can I resume default actions again?
回答1:
As per commented by @Prescott, the opposite of:
evt.preventDefault();
Could be:
Essentially equating to 'do default', since we're no longer preventing it.
Otherwise I'm inclined to point you to the answers provided by another comments and answers:
How to unbind a listener that is calling event.preventDefault() (using jQuery)?
How to reenable event.preventDefault?
Note that the second one has been accepted with an example solution, given by redsquare (posted here for a direct solution in case this isn't closed as duplicate):
$('form').submit( function(ev) {
ev.preventDefault();
//later you decide you want to submit
$(this).unbind('submit').submit()
});
回答2:
function(evt) {evt.preventDefault();}
and its opposite
function(evt) {return true;}
cheers!
回答3:
To process a command before continue a link from a click event in jQuery:
Eg: <a href="http://google.com/" class="myevent">Click me</a>
Prevent and follow through with jQuery:
$('a.myevent').click(function(event) {
event.preventDefault();
// Do my commands
if( myEventThingFirst() )
{
// then redirect to original location
window.location = this.href;
}
else
{
alert("Couldn't do my thing first");
}
});
Or simply run window.location = this.href; after the preventDefault();
回答4:
event.preventDefault(); //or event.returnValue = false;
and its opposite(standard) :
event.returnValue = true;
source: https://developer.mozilla.org/en-US/docs/Web/API/Event/returnValue
回答5:
OK ! it works for the click event :
$("#submit").click(function(e){
e.preventDefault();
-> block the click of the sumbit ... do what you want
$("#submit").unbind('click').click(); // the html click submit work now !
});
回答6:
I had to delay a form submission in jQuery in order to execute an asynchronous call. Here's the simplified code...
$("$theform").submit(function(e) {
e.preventDefault();
var $this = $(this);
$.ajax('/path/to/script.php',
{
type: "POST",
data: { value: $("#input_control").val() }
}).done(function(response) {
$this.unbind('submit').submit();
});
});
回答7:
I would suggest the following pattern:
document.getElementById("foo").onsubmit = function(e) {
if (document.getElementById("test").value == "test") {
return true;
} else {
e.preventDefault();
}
}
<form id="foo">
<input id="test"/>
<input type="submit"/>
</form>
...unless I'm missing something.
http://jsfiddle.net/DdvcX/
回答8:
There is no opposite method of event.preventDefault() to understand why you first have to look into what event.preventDefault() does when you call it.
Underneath the hood, the functionality for preventDefault is essentially calling a return false which halts any further execution. If you’re familiar with the old ways of Javascript, it was once in fashion to use return false for canceling events on things like form submits and buttons using return true (before jQuery was even around).
As you probably might have already worked out based on the simple explanation above: the opposite of event.preventDefault() is nothing. You just don’t prevent the event, by default the browser will allow the event if you are not preventing it.
See below for an explanation:
;(function($, window, document, undefined)) {
$(function() {
// By default deny the submit
var allowSubmit = false;
$("#someform").on("submit", function(event) {
if (!allowSubmit) {
event.preventDefault();
// Your code logic in here (maybe form validation or something)
// Then you set allowSubmit to true so this code is bypassed
allowSubmit = true;
}
});
});
})(jQuery, window, document);
In the code above you will notice we are checking if allowSubmit is false. 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.
回答9:
Here's something useful...
First of all we'll click on the link , run some code, and than we'll perform default action. This will be possible using event.currentTarget Take a look. Here we'll gonna try to access Google on a new tab, but before we need to run some code.
<a href="https://www.google.com.br" target="_blank" id="link">Google</a>
<script type="text/javascript">
$(document).ready(function() {
$("#link").click(function(e) {
// Prevent default action
e.preventDefault();
// Here you'll put your code, what you want to execute before default action
alert(123);
// Prevent infinite loop
$(this).unbind('click');
// Execute default action
e.currentTarget.click();
});
});
</script>
回答10:
This is what I used to set it:
$("body").on('touchmove', function(e){
e.preventDefault();
});
And to undo it:
$("body").unbind("touchmove");
回答11:
I supose the "opposite" would be to simulate an event. You could use .createEvent()
Following Mozilla's example:
function simulateClick() {
var evt = document.createEvent("MouseEvents");
evt.initMouseEvent("click", true, true, window,
0, 0, 0, 0, 0, false, false, false, false, 0, null);
var cb = document.getElementById("checkbox");
var cancelled = !cb.dispatchEvent(evt);
if(cancelled) {
// A handler called preventDefault
alert("cancelled");
} else {
// None of the handlers called preventDefault
alert("not cancelled");
}
}
Ref: document.createEvent
jQuery has .trigger() so you can trigger events on elements -- sometimes useful.
$('#foo').bind('click', function() {
alert($(this).text());
});
$('#foo').trigger('click');
回答12:
jquery on() could be another solution to this. escpacially when it comes to the use of namespaces.
jquery on() is just the current way of binding events ( instead of bind() ). off() is to unbind these. and when you use a namespace, you can add and remove multiple different events.
$( selector ).on("submit.my-namespace", function( event ) {
//prevent the event
event.preventDefault();
//cache the selector
var $this = $(this);
if ( my_condition_is_true ) {
//when 'my_condition_is_true' is met, the binding is removed and the event is triggered again.
$this.off("submit.my-namespace").trigger("submit");
}
});
now with the use of namespace, you could add multiple of these events and are able to remove those, depending on your needs.. while submit might not be the best example, this might come in handy on a click or keypress or whatever..
回答13:
you can use this after "preventDefault" method
//Here evt.target return default event (eg : defult url etc)
var defaultEvent=evt.target;
//Here we save default event ..
if("true")
{
//activate default event..
location.href(defaultEvent);
}
回答14:
You can always use this attached to some click event in your script:
location.href = this.href;
example of usage is:
jQuery('a').click(function(e) {
location.href = this.href;
});
回答15:
None of the solutions helped me here and I did this to solve my situation.
<a onclick="return clickEvent(event);" href="/contact-us">
And the function clickEvent(),
function clickEvent(event) {
event.preventDefault();
// do your thing here
// remove the onclick event trigger and continue with the event
event.target.parentElement.onclick = null;
event.target.parentElement.click();
}
回答16:
I have used the following code. It works fine for me.
$('a').bind('click', function(e) {
e.stopPropagation();
});
回答17:
this code worked for me to re-instantiate the event after i had used :
event.preventDefault(); to disable the event.
event.preventDefault = false;
来源：https://stackoverflow.com/questions/5651933/what-is-the-opposite-of-evt-preventdefault