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Javascript - Stop scrolling on certain links

For example,
Foo
Bar
...
<div id="foo"></div>
<div id="bar"></div>
Is there a way to selectively stop scrolling for certain elements?
In the example, above, what if I want the browser to not scroll to the #bar element if the anchor that has `href="#bar" is clicked?
Is this possible?

Use a click handler that returns false, which prevents the default click action.
Bar

yes, what you are looking for is how to prevent browser default behaviour
example (using jQuery)
$('a').on('click', function(event){
if($(this).attr('href') == '#bar'){
event.preventDefault();
}
});

Well, one of thr ways that I can suggest is to remove the href attribute in some specific circumstances. But removing href attribute may result in the anchor appear to be not clickable anymore...
If you want your anchor to still appear to be clickable:
'$("a").removeAttr("href").css("cursor","pointer");'
You may specify ids for specific anchor elements.

If you add a class or id to links that you don't want to scroll, you can then add an event listener to those links and prevent the default action on click.
HTML
Foo
Bar
...
<h2 id="foo">Foo</h2>
<h2 id="bar">Bar</h2>
Javascript
var blockedLinks = document.getElementsByClassName('blockedLink');
for (var i = 0; i < blockedLinks.length; i++) {
blockedLinks[i].addEventListener('click', function (e) {
e.preventDefault();
}, false);
}
Demo

jQuery return all page disabled and then enable

I would like a simple method to set the enteir page disabled (links,buttons etc ... all disabled) then i need to be able to re-enable all in the page.
is there a light way?

One option that is obvious for me is to set the "cover" layer:
<div id="cover"></div>
With style:
#cover {
position: fixed;
width: 100%;
height: 100%;
z-index: 100000;
}
If you need to disable everything, just make it visible with show method.
$("#cover").show();
It will work like this: http://jsfiddle.net/KEAh8/

This is not a light-weight method since it will have to scan the DOM to find every element, but it will work:
$("input, select, button, textarea").attr("disabled", true);
It depends on the size of your page to know if this is a good approach, and the selector could change depending on content. Reverse the attribute setting to enable everything again.
Edit:
As Porco pointed out, to disable the anchor tags you must prevent the default action, so add something like this:
$("a").click(function(e) {
e.preventDefault();
});

You can do:
$('*').attr('disabled', 'disabled').addClass('disabled')
So now we've disabled all inputs and added 'disabled' class to everything. Now we just want to disable links, I think this should work:
$('body').on('click', '.disabled', function(e) { e.preventDefault(); });
To renable everything simply:
$('*').attr('disabled', '').removeClass('disabled')

Anchor "javascript:void(0)" causing window.onbeforeunload to fire on IE

I am using a drop down widget called Chosen which has an anchor with a href javascript:void(0). When I click on the drop down it works but on IE it fires a new onbeforeunload event which is frustrating because the application confirms if you want to leave. And obviously you don't want to have those questions when you are inputting form data.
Is there a way to get rid of this problem without altering Chosen library?
Unfortunately this:
window.onbeforeunload = function (e) {
console.log(window.location);
};
Does not log javascript:void(0) either, so, I can't use it to check the target URL.
This behavior occurs in IE9 at least, and that's what I'm concerned (not the older IEs).

The only solution I can see is to add returning of false to the onclick event handler of the links. It will tell IE that you're not planning to change the page by clicking on the link.
Link
The same can be written this way:
<script>
function doSomething() {
// do Something
return false;
}
</script>
Link

I ended up listening to click events against the anchor and cancel the event to prevent onBeforeUnload from firing:
$chosen.find('.chzn-single').click(function() {
return false;
});

I know that this is pretty old...But I have come across this recently for my work. We are unfortunately still forced to support IE9. We are using Angular.js on this project that will dynamically load new content onto a page when the user clicks on an anchor tag with a data-ng-click.
In your example all you would have to do is pass the event and within the function prevent the default action and stop it from bubbling up. To do this all you would have to do is this:
// Inside the HTML
{...}
Link
{...}
<script>
function doSomething(evt) {
evt.preventDefault();
evt.stopPropagation();
// Do Something
};
</script>
{...}
In Angular all I did was the following:
// Inside the View
Add Stuff
// Inside the controller
function addStuff($event) {
$event.preventDefault();
$event.stopPropagation();
// Do Something
};
I hope that this isn't too late and I hope that it helps others.

Had the same problem. Just found your question. My solution is, you need to add onclick attribute to every chosen dropdown list anchor tag and call window.onbeforeunload = null
In my case, I've put
$(".chzn-single").attr("onclick", "window.onbeforeunload = null;");
After setting up chosen library and it works fine

don't use href's for this. A simple solution with minimal extra work:
i prefer to use a CSS class that simulates an href, obviously you will change the color and styling of this class to fit your website, but for this purposes, it's the standard blue underlined link
<style>
.linkSimulate
{
cursor: pointer;
COLOR: blue;
text-decoration: underline;
}
</style>
then use a simple anchor
<a onclick = "do_save();" class ="linkSimulate">Link</a>

Even if this question is old, i've anhanced the answer of #Bartosz, fixing the issue in the comment of #Oiva Eskola:
Wouldn't this prevent the window.onbeforeunload from working after clicking a chosen link element? – var thisOnClick;
Below is my solution to properly create the HTML onclick property, to not override or cancel the event:
var thisOnClick;
$.each( $(' .container a '), function(){
thisOnClick = $(this).attr('onclick');
if ( typeof thisOnClick == 'undefined' ) {
$(this).attr('onclick', 'window.onbeforeunload = null;');
} else if ( typeof thisOnClick == 'string' && thisOnClick.indexOf('window.onbeforeunload') == -1 ) {
$(this).attr('onclick', thisOnClick + 'window.onbeforeunload = null;');
}
});

Event detect when css property changed using Jquery

Is there a way to detect if the "display" css property of an element is changed (to whether none or block or inline-block...)? if not, any plugin? Thanks

Note
Mutation events have been deprecated since this post was written, and may not be supported by all browsers. Instead, use a mutation observer.
Yes you can. DOM L2 Events module defines mutation events; one of them - DOMAttrModified is the one you need. Granted, these are not widely implemented, but are supported in at least Gecko and Opera browsers.
Try something along these lines:
document.documentElement.addEventListener('DOMAttrModified', function(e){
if (e.attrName === 'style') {
console.log('prevValue: ' + e.prevValue, 'newValue: ' + e.newValue);
}
}, false);
document.documentElement.style.display = 'block';
You can also try utilizing IE's "propertychange" event as a replacement to DOMAttrModified. It should allow to detect style changes reliably.

You can use attrchange jQuery plugin. The main function of the plugin is to bind a listener function on attribute change of HTML elements.
Code sample:
$("#myDiv").attrchange({
trackValues: true, // set to true so that the event object is updated with old & new values
callback: function(evnt) {
if(evnt.attributeName == "display") { // which attribute you want to watch for changes
if(evnt.newValue.search(/inline/i) == -1) {
// your code to execute goes here...
}
}
}
});

You can use jQuery's css function to test the CSS properties, eg. if ($('node').css('display') == 'block').
Colin is right, that there is no explicit event that gets fired when a specific CSS property gets changed. But you may be able to flip it around, and trigger an event that sets the display, and whatever else.
Also consider using adding CSS classes to get the behavior you want. Often you can add a class to a containing element, and use CSS to affect all elements. I often slap a class onto the body element to indicate that an AJAX response is pending. Then I can use CSS selectors to get the display I want.
Not sure if this is what you're looking for.

For properties for which css transition will affect, can use transitionend event, example for z-index:
$(".observed-element").on("webkitTransitionEnd transitionend", function(e) {
console.log("end", e);
alert("z-index changed");
});
$(".changeButton").on("click", function() {
console.log("click");
document.querySelector(".observed-element").style.zIndex = (Math.random() * 1000) | 0;
});
.observed-element {
transition: z-index 1ms;
-webkit-transition: z-index 1ms;
}
div {
width: 100px;
height: 100px;
border: 1px solid;
position: absolute;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button class="changeButton">change z-index</button>
<div class="observed-element"></div>

You can't. CSS does not support "events". Dare I ask what you need it for? Check out this post here on SO. I can't think of a reason why you would want to hook up an event to a style change. I'm assuming here that the style change is triggered somwhere else by a piece of javascript. Why not add extra logic there?

Using jQuery to test if an input has focus

On the front page of a site I am building, several <div>s use the CSS :hover pseudo-class to add a border when the mouse is over them. One of the <div>s contains a <form> which, using jQuery, will keep the border if an input within it has focus. This works perfectly except that IE6 does not support :hover on any elements other than <a>s. So, for this browser only we are using jQuery to mimic CSS :hover using the $(#element).hover() method. The only problem is, now that jQuery handles both the form focus() and hover(), when an input has focus then the user moves the mouse in and out, the border goes away.
I was thinking we could use some kind of conditional to stop this behavior. For instance, if we tested on mouse out if any of the inputs had focus, we could stop the border from going away. AFAIK, there is no :focus selector in jQuery, so I'm not sure how to make this happen. Any ideas?

jQuery 1.6+
jQuery added a :focus selector so we no longer need to add it ourselves. Just use $("..").is(":focus")
jQuery 1.5 and below
Edit: As times change, we find better methods for testing focus, the new favorite is this gist from Ben Alman:
jQuery.expr[':'].focus = function( elem ) {
return elem === document.activeElement && ( elem.type || elem.href );
};
Quoted from Mathias Bynens here:
Note that the (elem.type || elem.href) test was added to filter out false positives like body. This way, we make sure to filter out all elements except form controls and hyperlinks.
You're defining a new selector. See Plugins/Authoring. Then you can do:
if ($("...").is(":focus")) {
...
}
or:
$("input:focus").doStuff();
Any jQuery
If you just want to figure out which element has focus, you can use
$(document.activeElement)
If you aren't sure if the version will be 1.6 or lower, you can add the :focus selector if it is missing:
(function ( $ ) {
var filters = $.expr[":"];
if ( !filters.focus ) {
filters.focus = function( elem ) {
return elem === document.activeElement && ( elem.type || elem.href );
};
}
})( jQuery );

CSS:
.focus {
border-color:red;
}
JQuery:
$(document).ready(function() {
$('input').blur(function() {
$('input').removeClass("focus");
})
.focus(function() {
$(this).addClass("focus")
});
});

Here’s a more robust answer than the currently accepted one:
jQuery.expr[':'].focus = function(elem) {
return elem === document.activeElement && (elem.type || elem.href);
};
Note that the (elem.type || elem.href) test was added to filter out false positives like body. This way, we make sure to filter out all elements except form controls and hyperlinks.
(Taken from this gist by Ben Alman.)

April 2015 Update
Since this question has been around a while, and some new conventions have come into play, I feel that I should mention the .live method has been depreciated.
In its place, the .on method has now been introduced.
Their documentation is quite useful in explaining how it works;
The .on() method attaches event handlers to the currently selected set
of elements in the jQuery object. As of jQuery 1.7, the .on() method
provides all functionality required for attaching event handlers. For
help in converting from older jQuery event methods, see .bind(),
.delegate(), and .live().
So, in order for you to target the 'input focused' event, you can use this in a script. Something like:
$('input').on("focus", function(){
//do some stuff
});
This is quite robust and even allows you to use the TAB key as well.

I'm not entirely sure what you're after but this sounds like it can be achieved by storing the state of the input elements (or the div?) as a variable:
$('div').each(function(){
var childInputHasFocus = false;
$(this).hover(function(){
if (childInputHasFocus) {
// do something
} else { }
}, function() {
if (childInputHasFocus) {
// do something
} else { }
});
$('input', this)
.focus(function(){
childInputHasFocus = true;
})
.blur(function(){
childInputHasFocus = false;
});
});

An alternative to using classes to mark the state of an element is the internal data store functionality.
P.S.: You are able to store booleans and whatever you desire using the data() function. It's not just about strings :)
$("...").mouseover(function ()
{
// store state on element
}).mouseout(function ()
{
// remove stored state on element
});
And then it's just a matter of accessing the state of elements.

if anyone cares there is a much better way to capture focus now, $(foo).focus(...)
http://api.jquery.com/focus/

Have you thought about using mouseOver and mouseOut to simulate this. Also look into mouseEnter and mouseLeave

Keep track of both states (hovered, focused) as true/false flags, and whenever one changes, run a function that removes border if both are false, otherwise shows border.
So: onfocus sets focused = true, onblur sets focused = false. onmouseover sets hovered = true, onmouseout sets hovered = false. After each of these events run a function that adds/removes border.

As far as I know, you can't ask the browser if any input on the screen has focus, you have to set up some sort of focus tracking.
I usually have a variable called "noFocus" and set it to true. Then I add a focus event to all inputs that makes noFocus false. Then I add a blur event to all inputs that set noFocus back to true.
I have a MooTools class that handles this quite easily, I'm sure you could create a jquery plugin to do the same.
Once that's created, you could do check noFocus before doing any border swapping.

There is no :focus, but there is :selected
http://docs.jquery.com/Selectors/selected
but if you want to change how things look based on what is selected you should probably be working with the blur events.
http://docs.jquery.com/Events/blur

There is a plugin to check if an element is focused: http://plugins.jquery.com/project/focused
$('input').each(function(){
if ($(this) == $.focused()) {
$(this).addClass('focused');
}
})

I had a .live("focus") event set to select() (highlight) the contents of a text input so that the user wouldn't have to select it before typing a new value.
$(formObj).select();
Because of quirks between different browsers, the select would sometimes be superseded by the click that caused it, and it would deselect the contents right after in favor of placing the cursor within the text field (worked mostly ok in FF but failed in IE)
I thought I could solve this by putting a slight delay on the select...
setTimeout(function(){$(formObj).select();},200);
This worked fine and the select would persist, but a funny problem arose.. If you tabbed from one field to the next, the focus would switch to the next field before the select took place. Since select steals focus, the focus would then go back and trigger a new "focus" event. This ended up in a cascade of input selects dancing all over the screen.
A workable solution would be to check that the field still has focus before executing the select(), but as mentioned, there's no simple way to check... I ended up just dispensing with the whole auto highlight, rather than turning what should be a single jQuery select() call into a huge function laden with subroutines...

What I wound up doing is creating an arbitrary class called .elementhasfocus which is added and removed within the jQuery focus() function. When the hover() function runs on mouse out, it checks for .elementhasfocus:
if(!$("#quotebox").is(".boxhasfocus")) $(this).removeClass("box_border");
So if it doesn't have that class (read: no elements within the div have focus) the border is removed. Otherwise, nothing happens.

Simple
<input type="text" />
<script>
$("input").focusin(function() {
alert("I am in Focus");
});
</script>