Following is my JavaScript (mootools) code:
$('orderNowForm').addEvent('submit', function (event) {
event.preventDefault();
allFilled = false;
$$(".required").each(function (inp) {
if (inp.getValue() != '') {
allFilled = true;
}
});
if (!allFilled) {
$$(".errormsg").setStyle('display', '');
return;
} else {
$$('.defaultText').each(function (input) {
if (input.getValue() == input.getAttribute('title')) {
input.setAttribute('value', '');
}
});
}
this.send({
onSuccess: function () {
$('page_1_table').setStyle('display', 'none');
$('page_2_table').setStyle('display', 'none');
$('page_3_table').setStyle('display', '');
}
});
});
In all browsers except IE, this works fine. But in IE, this causes an error. I have IE8 so while using its JavaScript debugger, I found out that the event object does not have a preventDefault method which is causing the error and so the form is getting submitted. The method is supported in case of Firefox (which I found out using Firebug).
Any Help?
in IE, you can use
event.returnValue = false;
to achieve the same result.
And in order not to get an error, you can test for the existence of preventDefault:
if(event.preventDefault) event.preventDefault();
You can combine the two with:
event.preventDefault ? event.preventDefault() : (event.returnValue = false);
If you bind the event through mootools' addEvent function your event handler will get a fixed (augmented) event passed as the parameter. It will always contain the preventDefault() method.
Try out this fiddle to see the difference in event binding.
http://jsfiddle.net/pFqrY/8/
// preventDefault always works
$("mootoolsbutton").addEvent('click', function(event) {
alert(typeof(event.preventDefault));
});
// preventDefault missing in IE
<button
id="htmlbutton"
onclick="alert(typeof(event.preventDefault));">
button</button>
For all jQuery users out there you can fix an event when needed. Say that you used HTML onclick=".." and get a IE specific event that lacks preventDefault(), just use this code to get it.
e = $.event.fix(e);
After that e.preventDefault(); works fine.
I know this is quite an old post but I just spent some time trying to make this work in IE8.
It appears that there are some differences in IE8 versions because solutions posted here and in other threads didn't work for me.
Let's say that we have this code:
$('a').on('click', function(event) {
event.preventDefault ? event.preventDefault() : event.returnValue = false;
});
In my IE8 preventDefault() method exists because of jQuery, but is not working (probably because of the point below), so this will fail.
Even if I set returnValue property directly to false:
$('a').on('click', function(event) {
event.returnValue = false;
event.preventDefault();
});
This also won't work, because I just set some property of jQuery custom event object.
Only solution that works for me is to set property returnValue of global variable event like this:
$('a').on('click', function(event) {
if (window.event) {
window.event.returnValue = false;
}
event.preventDefault();
});
Just to make it easier for someone who will try to convince IE8 to work. I hope that IE8 will die horribly in painful death soon.
UPDATE:
As sv_in points out, you could use event.originalEvent to get original event object and set returnValue property in the original one. But I haven't tested it in my IE8 yet.
Mootools redefines preventDefault in Event objects. So your code should work fine on every browser. If it doesn't, then there's a problem with ie8 support in mootools.
Did you test your code on ie6 and/or ie7?
The doc says
Every event added with addEvent gets the mootools method automatically, without the need to manually instance it.
but in case it doesn't, you might want to try
new Event(event).preventDefault();
if (e.preventDefault) {
e.preventDefault();
} else {
e.returnValue = false;
}
Tested on IE 9 and Chrome.
To disable a keyboard key after IE9, use : e.preventDefault();
To disable a regular keyboard key under IE7/8, use : e.returnValue = false; or return false;
If you try to disable a keyboard shortcut (with Ctrl, like Ctrl+F) you need to add those lines :
try {
e.keyCode = 0;
}catch (e) {}
Here is a full example for IE7/8 only :
document.attachEvent("onkeydown", function () {
var e = window.event;
//Ctrl+F or F3
if (e.keyCode === 114 || (e.ctrlKey && e.keyCode === 70)) {
//Prevent for Ctrl+...
try {
e.keyCode = 0;
}catch (e) {}
//prevent default (could also use e.returnValue = false;)
return false;
}
});
Reference : How to disable keyboard shortcuts in IE7 / IE8
Here's a function I've been testing with jquery 1.3.2 and 09-18-2009's nightly build. Let me know your results with it. Everything executes fine on this end in Safari, FF, Opera on OSX. It is exclusively for fixing a problematic IE8 bug, and may have unintended results:
function ie8SafePreventEvent(e) {
if (e.preventDefault) {
e.preventDefault()
} else {
e.stop()
};
e.returnValue = false;
e.stopPropagation();
}
Usage:
$('a').click(function (e) {
// Execute code here
ie8SafePreventEvent(e);
return false;
})
preventDefault is a widespread standard; using an adhoc every time you want to be compliant with old IE versions is cumbersome, better to use a polyfill:
if (typeof Event.prototype.preventDefault === 'undefined') {
Event.prototype.preventDefault = function (e, callback) {
this.returnValue = false;
};
}
This will modify the prototype of the Event and add this function, a great feature of javascript/DOM in general. Now you can use e.preventDefault with no problem.
return false in your listener should work in all browsers.
$('orderNowForm').addEvent('submit', function () {
// your code
return false;
}
FWIW, in case anyone revisits this question later, you might also check what you are handing to your onKeyPress handler function.
I ran into this error when I mistakenly passed onKeyPress(this) instead of onKeyPress(event).
Just something else to check.
I was helped by a method with a function check. This method works in IE8
if(typeof e.preventDefault == 'function'){
e.preventDefault();
} else {
e.returnValue = false;
}
Related
The book that I am learning JS from has code like below :
function check(e) {
if (!e){
e = window.event; // for IE
}
var target = e.target || e.srcTarget;
if (**e.preventDefault**){
e.preventDefault() ;
}
target.returnValue = false;
}
var el = document.getElementById("list");
el.addEventListener("click", check , false);
I understand that preventDefault is a method and not a property . I did not understand how they are doing a e.preventDefault in the if condition .I checked in chrome and did not find any property called preventDefault for e . There is a function under proto called preventDefault. Am I correct in assuming that all methods can be changed to a property removing the () and you can use it in your code to test if that method is available or not ?
the double asterisks should not be there.
if(e.preventDefault) will work because if checks if the passed argument isn't null. So when preventDefault function will be defined, the condition will be true.
This is just for checking cross browser support. IE 8 or under won't support preventDefault, they use returnValue.
//check preventDefault function is exists in event handler 'e'
if (e.preventDefault) {
// if browser support preventDefault, call preventDefault();
e.preventDefault();
}
I have already gone through this question
event.preventDefault() vs. return false
But didn't find my solution. Actually i am using javascript function to go back to previous page that is working fine on click of
<img src="images/backbtn.png">
function
function goBack(){
window.history.back();
}
When i click on <a> it includes # in url which i want to prevent. In jquery we use preventDefault() to stop the default event of an element but is there any similar function in javascript to stop it.
I know i can use javascript:void(0) in href which will solve the problem but there can be many other instances so i want to know about function in javascript.
I tried using return false; but it i write this on top like this
function goBack(){
return false;
window.history.back();
}
Then it stops the function to execute and if i write like this
function goBack(){
window.history.back();
return false;
}
Then no effect from this return false;. I am sure there is some in javascript as jquery is generated from javascript.
Any help would be appreciated. Thanks in advance!
As far as I know, preventDefault() also is a native JS function, so you can use it without jQuery and get same result.
You can read more about it here: MDN: Event.preventDefault()
event.preventDefault() works both in Javasccript and Jquery
If getting the # is the problem and for some reason you really want to use only preventDefault() then you must pass the event into the function and then inside the function use event.preventDefault()
<img src="images/backbtn.png">
Then in your Javascript use this passed event and stop the default behaviour.
function goBack(event){
event.preventDefault();
window.history.back();
}
To add to the answers, return false in jquery does both event.preventDefault and event.stopPropagation()
From jquery source code, jquery.event.dispatch
if ( ret !== undefined ) {
if ( (event.result = ret) === false ) {
event.preventDefault();
event.stopPropagation();
}
}
Both preventDefault and stopPropagation are available in Javascript.
For IE < 9, event.stopPropagation can be done by event.cancelBubble = true
and event.preventDefault can be done by event.returnValue = false
preventDefault exists in javascript, but if you are interested in a jQuery like solution you need to take care of compatibility issues.
A different solution, considering the compatibility issues with old browsers, is:
function goBack(evt){
var e = evt || window.event;
if (e !== undefined) {
if (e.preventDefault) {
e.preventDefault();
} else { // IE
e.returnValue = false;
}
}
window.history.back();
}
<img src="images/backbtn.png">
The following works fine everywhere except in IE 11:
if( event.keyCode == 18 )
{
event.preventDefault ? event.preventDefault() : event.returnValue = false
altcurrentstate = "keyisdown";
Xmouse = x;
Ymouse= y;
return false;
}
I also tried the others ways offered in this site but nope, can't seems to preventDefault in IE 11 no matter what, for the alt and arrow keys. The event.returnValue = false; trick is not working either. Not working with return false either...
Try actually return false in your callback function.
Perhaps you need to make your event cancelable using the initEvent() method.
According to the remarks at the bottom of this page:
If you cannot cancel the event, calling IDOMEvent::preventDefault has no effect.
When you create a custom event by using the IDocumentEvent::createEvent method, you can set the IDOMEvent::cancelable property by using the IDOMEvent::initEvent method.
I want to register keypress events for a document using javascript.
I have used:
document.attachEvent("onkeydown", my_onkeydown_handler);
It works fine with IE,
but not with Firefox and Chrome.
I also tried:
document.addEventListener("onkeydown", my_onkeydown_handler, true);
// (with false value also)
But it still doesn't work with Firefox and Chrome.
Is there a solution, am I missing something?
You are looking for:
EDIT:
Javascript:
document.addEventListener("keydown", keyDownTextField, false);
function keyDownTextField(e) {
var keyCode = e.keyCode;
if(keyCode==13) {
alert("You hit the enter key.");
} else {
alert("Oh no you didn't.");
}
}
DEMO: JSFIDDLE
You are probably looking for:
document.body.addEventListener('keydown', function (e) {
alert('hello world');
});
But it is almost certainly going to be worth your time to use an existing library to abstract over the problems of the many browsers out there.
Please go through following links for detailed description.
https://developer.mozilla.org/en-US/docs/DOM/element.addEventListener?redirectlocale=en-US&redirectslug=DOM%3Aelement.addEventListener
http://www.reloco.com.ar/mozilla/compat.html
In short, write handler as
function myFunction(e)
{
///For IE
if(!e)
e=window.event;
// use e as event in rest of code.
}
My code works fine in FF/Chrome/Everything except IE(failed in both 7/8, didn't bother going furthur down). Due to restrictions, I cannot use jQuery and am hard-coding the Javascript. The issue is with IE, I am getting "preventDefault is null or not an object". Hoping one of you has the answer, and here's relevant code:
AddEvent Method:
function addEvent( obj, type, fn ) {
if ( obj.attachEvent ) {
obj['e'+type+fn] = fn;
obj[type+fn] = function(){obj['e'+type+fn]( window.event );}
obj.attachEvent( 'on'+type, obj[type+fn] );
} else
obj.addEventListener( type, fn, false );
};
Event handler throwing error:
function mousedown(e){
if(e.preventDefault){
e.preventDefault();
} else {
e.returnValue = false;
e.cancelBubble=true;
}
//Processing
};
Also DOCTYPE and charset are both set on the calling HTML page. Any ideas would be appreciated. The error is thrown in the if statement for the mousedown method.
EDIT:
Due to the fact that grabbing window.event did "fix" the main issue, I discovered the problem was a different section of code. Basically I am adding a element ontop of a pre-placed element, and then registering mousedown/mousemove events to that div. When firing the event on the <div>, THAT'S where the error is thrown.
Could this be something due to the fact that I have events registered to 2
rect = document.createElement('div');
rect.className='square';
rect.id='chooser_rectangle';
rect.style.left=initx+'px';
rect.style.top=inity+'px';
addEvent(rect,"mousemove",mousemove);
addEvent(rect,"mousedown",mousedown);
In IE the event object is not passed as the first argument to an event handler. Instead it is a global variable:
function mousedown(e){
var evt = e || window.event; // IE compatibility
if(evt.preventDefault){
evt.preventDefault();
}else{
evt.returnValue = false;
evt.cancelBubble=true;
}
//Processing
};
IE has a different event model to other browsers (even IE8). In IE you would call this to do the same thing:
event.returnValue = false;
You need to determine what the browser supports and call the correct method. So first check if event.returnValue is set, if so then call it, otherwise call preventDefault().