I'm using jQuery in my site and I would like to trigger certain actions when a certain div is made visible.
Is it possible to attach some sort of "isvisible" event handler to arbitrary divs and have certain code run when they the div is made visible?
I would like something like the following pseudocode:
$(function() {
$('#contentDiv').isvisible(function() {
alert("do something");
});
});
The alert("do something") code should not fire until the contentDiv is actually made visible.
Thanks.
You could always add to the original .show() method so you don't have to trigger events every time you show something or if you need it to work with legacy code:
Jquery extension:
jQuery(function($) {
var _oldShow = $.fn.show;
$.fn.show = function(speed, oldCallback) {
return $(this).each(function() {
var obj = $(this),
newCallback = function() {
if ($.isFunction(oldCallback)) {
oldCallback.apply(obj);
}
obj.trigger('afterShow');
};
// you can trigger a before show if you want
obj.trigger('beforeShow');
// now use the old function to show the element passing the new callback
_oldShow.apply(obj, [speed, newCallback]);
});
}
});
Usage example:
jQuery(function($) {
$('#test')
.bind('beforeShow', function() {
alert('beforeShow');
})
.bind('afterShow', function() {
alert('afterShow');
})
.show(1000, function() {
alert('in show callback');
})
.show();
});
This effectively lets you do something beforeShow and afterShow while still executing the normal behavior of the original .show() method.
You could also create another method so you don't have to override the original .show() method.
The problem is being addressed by DOM mutation observers. They allow you to bind an observer (a function) to events of changing content, text or attributes of dom elements.
With the release of IE11, all major browsers support this feature, check http://caniuse.com/mutationobserver
The example code is a follows:
$(function() {
$('#show').click(function() {
$('#testdiv').show();
});
var observer = new MutationObserver(function(mutations) {
alert('Attributes changed!');
});
var target = document.querySelector('#testdiv');
observer.observe(target, {
attributes: true
});
});
<div id="testdiv" style="display:none;">hidden</div>
<button id="show">Show hidden div</button>
<script type="text/javascript" src="https://code.jquery.com/jquery-1.9.1.min.js"></script>
There is no native event you can hook into for this however you can trigger an event from your script after you have made the div visible using the .trigger function
e.g
//declare event to run when div is visible
function isVisible(){
//do something
}
//hookup the event
$('#someDivId').bind('isVisible', isVisible);
//show div and trigger custom event in callback when div is visible
$('#someDivId').show('slow', function(){
$(this).trigger('isVisible');
});
You can use jQuery's Live Query plugin.
And write code as follows:
$('#contentDiv:visible').livequery(function() {
alert("do something");
});
Then everytime the contentDiv is visible, "do something" will be alerted!
redsquare's solution is the right answer.
But as an IN-THEORY solution you can write a function which is selecting the elements classed by .visibilityCheck (not all visible elements) and check their visibility property value; if true then do something.
Afterward, the function should be performed periodically using the setInterval() function. You can stop the timer using the clearInterval() upon successful call-out.
Here's an example:
function foo() {
$('.visibilityCheck').each(function() {
if ($(this).is(':visible')){
// do something
}
});
}
window.setInterval(foo, 100);
You can also perform some performance improvements on it, however, the solution is basically absurd to be used in action. So...
The following code (pulled from http://maximeparmentier.com/2012/11/06/bind-show-hide-events-with-jquery/) will enable you to use $('#someDiv').on('show', someFunc);.
(function ($) {
$.each(['show', 'hide'], function (i, ev) {
var el = $.fn[ev];
$.fn[ev] = function () {
this.trigger(ev);
return el.apply(this, arguments);
};
});
})(jQuery);
If you want to trigger the event on all elements (and child elements) that are actually made visible, by $.show, toggle, toggleClass, addClass, or removeClass:
$.each(["show", "toggle", "toggleClass", "addClass", "removeClass"], function(){
var _oldFn = $.fn[this];
$.fn[this] = function(){
var hidden = this.find(":hidden").add(this.filter(":hidden"));
var result = _oldFn.apply(this, arguments);
hidden.filter(":visible").each(function(){
$(this).triggerHandler("show"); //No bubbling
});
return result;
}
});
And now your element:
$("#myLazyUl").bind("show", function(){
alert(this);
});
You could add overrides to additional jQuery functions by adding them to the array at the top (like "attr")
a hide/show event trigger based on Glenns ideea:
removed toggle because it fires show/hide and we don't want 2fires for one event
$(function(){
$.each(["show","hide", "toggleClass", "addClass", "removeClass"], function(){
var _oldFn = $.fn[this];
$.fn[this] = function(){
var hidden = this.find(":hidden").add(this.filter(":hidden"));
var visible = this.find(":visible").add(this.filter(":visible"));
var result = _oldFn.apply(this, arguments);
hidden.filter(":visible").each(function(){
$(this).triggerHandler("show");
});
visible.filter(":hidden").each(function(){
$(this).triggerHandler("hide");
});
return result;
}
});
});
I had this same problem and created a jQuery plugin to solve it for our site.
https://github.com/shaunbowe/jquery.visibilityChanged
Here is how you would use it based on your example:
$('#contentDiv').visibilityChanged(function(element, visible) {
alert("do something");
});
What helped me here is recent ResizeObserver spec polyfill:
const divEl = $('#section60');
const ro = new ResizeObserver(() => {
if (divEl.is(':visible')) {
console.log("it's visible now!");
}
});
ro.observe(divEl[0]);
Note that it's crossbrowser and performant (no polling).
Just bind a trigger with the selector and put the code into the trigger event:
jQuery(function() {
jQuery("#contentDiv:hidden").show().trigger('show');
jQuery('#contentDiv').on('show', function() {
console.log('#contentDiv is now visible');
// your code here
});
});
Use jQuery Waypoints :
$('#contentDiv').waypoint(function() {
alert('do something');
});
Other examples on the site of jQuery Waypoints.
I did a simple setinterval function to achieve this. If element with class div1 is visible, it sets div2 to be visible. I know not a good method, but a simple fix.
setInterval(function(){
if($('.div1').is(':visible')){
$('.div2').show();
}
else {
$('.div2').hide();
}
}, 100);
You can also try jQuery appear plugin as mentioned in parallel thread https://stackoverflow.com/a/3535028/741782
This support easing and trigger event after animation done! [tested on jQuery 2.2.4]
(function ($) {
$.each(['show', 'hide', 'fadeOut', 'fadeIn'], function (i, ev) {
var el = $.fn[ev];
$.fn[ev] = function () {
var result = el.apply(this, arguments);
var _self=this;
result.promise().done(function () {
_self.triggerHandler(ev, [result]);
//console.log(_self);
});
return result;
};
});
})(jQuery);
Inspired By http://viralpatel.net/blogs/jquery-trigger-custom-event-show-hide-element/
There is a jQuery plugin available for watching change in DOM attributes,
https://github.com/darcyclarke/jQuery-Watch-Plugin
The plugin wraps All you need do is bind MutationObserver
You can then use it to watch the div using:
$("#selector").watch('css', function() {
console.log("Visibility: " + this.style.display == 'none'?'hidden':'shown'));
//or any random events
});
Hope this will do the job in simplest manner:
$("#myID").on('show').trigger('displayShow');
$('#myID').off('displayShow').on('displayShow', function(e) {
console.log('This event will be triggered when myID will be visible');
});
I changed the hide/show event trigger from Catalint based on Glenns idea.
My problem was that I have a modular application. I change between modules showing and hiding divs parents. Then when I hide a module and show another one, with his method I have a visible delay when I change between modules. I only need sometimes to liten this event, and in some special childs. So I decided to notify only the childs with the class "displayObserver"
$.each(["show", "hide", "toggleClass", "addClass", "removeClass"], function () {
var _oldFn = $.fn[this];
$.fn[this] = function () {
var hidden = this.find(".displayObserver:hidden").add(this.filter(":hidden"));
var visible = this.find(".displayObserver:visible").add(this.filter(":visible"));
var result = _oldFn.apply(this, arguments);
hidden.filter(":visible").each(function () {
$(this).triggerHandler("show");
});
visible.filter(":hidden").each(function () {
$(this).triggerHandler("hide");
});
return result;
}
});
Then when a child wants to listen for "show" or "hide" event I have to add him the class "displayObserver", and when It does not want to continue listen it, I remove him the class
bindDisplayEvent: function () {
$("#child1").addClass("displayObserver");
$("#child1").off("show", this.onParentShow);
$("#child1").on("show", this.onParentShow);
},
bindDisplayEvent: function () {
$("#child1").removeClass("displayObserver");
$("#child1").off("show", this.onParentShow);
},
I wish help
One way to do this.
Works only on visibility changes that are made by css class change, but can be extended to watch for attribute changes too.
var observer = new MutationObserver(function(mutations) {
var clone = $(mutations[0].target).clone();
clone.removeClass();
for(var i = 0; i < mutations.length; i++){
clone.addClass(mutations[i].oldValue);
}
$(document.body).append(clone);
var cloneVisibility = $(clone).is(":visible");
$(clone).remove();
if (cloneVisibility != $(mutations[0].target).is(":visible")){
var visibilityChangedEvent = document.createEvent('Event');
visibilityChangedEvent.initEvent('visibilityChanged', true, true);
mutations[0].target.dispatchEvent(visibilityChangedEvent);
}
});
var targets = $('.ui-collapsible-content');
$.each(targets, function(i,target){
target.addEventListener('visibilityChanged',VisbilityChanedEventHandler});
target.addEventListener('DOMNodeRemovedFromDocument',VisbilityChanedEventHandler });
observer.observe(target, { attributes: true, attributeFilter : ['class'], childList: false, attributeOldValue: true });
});
function VisbilityChanedEventHandler(e){console.log('Kaboom babe'); console.log(e.target); }
my solution:
; (function ($) {
$.each([ "toggle", "show", "hide" ], function( i, name ) {
var cssFn = $.fn[ name ];
$.fn[ name ] = function( speed, easing, callback ) {
if(speed == null || typeof speed === "boolean"){
var ret=cssFn.apply( this, arguments )
$.fn.triggerVisibleEvent.apply(this,arguments)
return ret
}else{
var that=this
var new_callback=function(){
callback.call(this)
$.fn.triggerVisibleEvent.apply(that,arguments)
}
var ret=this.animate( genFx( name, true ), speed, easing, new_callback )
return ret
}
};
});
$.fn.triggerVisibleEvent=function(){
this.each(function(){
if($(this).is(':visible')){
$(this).trigger('visible')
$(this).find('[data-trigger-visible-event]').triggerVisibleEvent()
}
})
}
})(jQuery);
example usage:
if(!$info_center.is(':visible')){
$info_center.attr('data-trigger-visible-event','true').one('visible',processMoreLessButton)
}else{
processMoreLessButton()
}
function processMoreLessButton(){
//some logic
}
$( window ).scroll(function(e,i) {
win_top = $( window ).scrollTop();
win_bottom = $( window ).height() + win_top;
//console.log( win_top,win_bottom );
$('.onvisible').each(function()
{
t = $(this).offset().top;
b = t + $(this).height();
if( t > win_top && b < win_bottom )
alert("do something");
});
});
$(function() {
$(document).click(function (){
if ($('#contentDiv').is(':visible')) {
alert("Visible");
} else {
alert("Hidden");
}
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="contentDiv">Test I'm here</div>
<button onclick="$('#contentDiv').toggle();">Toggle the div</button>
<div id="welcometo">Özhan</div>
<input type="button" name="ooo"
onclick="JavaScript:
if(document.all.welcometo.style.display=='none') {
document.all.welcometo.style.display='';
} else {
document.all.welcometo.style.display='none';
}">
This code auto control not required query visible or unvisible control
Related
I would like to have something like:
$('#myDiv').bind('class "submission ok" added'){
alert('class "submission ok" has been added');
});
There is no event raised when a class changes. The alternative is to manually raise an event when you programatically change the class:
$someElement.on('event', function() {
$('#myDiv').addClass('submission-ok').trigger('classChange');
});
// in another js file, far, far away
$('#myDiv').on('classChange', function() {
// do stuff
});
UPDATE - 2015
This question seems to be gathering some visitors, so here is an update with an approach which can be used without having to modify existing code using the new MutationObserver:
var $div = $("#foo");
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
var attributeValue = $(mutation.target).prop(mutation.attributeName);
console.log("Class attribute changed to:", attributeValue);
});
});
observer.observe($div[0], {
attributes: true,
attributeFilter: ['class']
});
$div.addClass('red');
.red {
color: #C00;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<div id="foo" class="bar">#foo.bar</div>
Be aware that the MutationObserver is only available for newer browsers, specifically Chrome 26, FF 14, IE 11, Opera 15 and Safari 6. See MDN for more details. If you need to support legacy browsers then you will need to use the method I outlined in my first example.
UPDATE - 2022
Here's an implementation of the above wrapped in to a jQuery extension method:
// extension method:
$.fn.classChange = function(cb) {
return $(this).each((_, el) => {
new MutationObserver(mutations => {
mutations.forEach(mutation => cb && cb(mutation.target, $(mutation.target).prop(mutation.attributeName)));
}).observe(el, {
attributes: true,
attributeFilter: ['class'] // only listen for class attribute changes
});
});
}
// usage:
const $foo = $("#foo").classChange((el, newClass) => console.log(`#${el.id} had its class updated to: ${newClass}`));
const $fizz = $("#fizz").classChange((el, newClass) => console.log(`#${el.id} had its class updated to: ${newClass}`));
// trigger
$('#trigger').on('click', () => {
$foo.removeClass('red');
$fizz.addClass('green dark-bg');
});
.red {
color: #C00;
}
.green {
color: #0C0;
}
.dark-bg {
background-color: #666;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<button id="trigger">Change classes</button>
<div id="foo" class="bar red">#foo.bar</div>
<div id="fizz" class="buzz">#fizz.buzz</div>
You could replace the original jQuery addClass and removeClass functions with your own that would call the original functions and then trigger a custom event. (Using a self-invoking anonymous function to contain the original function reference)
(function( func ) {
$.fn.addClass = function() { // replace the existing function on $.fn
func.apply( this, arguments ); // invoke the original function
this.trigger('classChanged'); // trigger the custom event
return this; // retain jQuery chainability
}
})($.fn.addClass); // pass the original function as an argument
(function( func ) {
$.fn.removeClass = function() {
func.apply( this, arguments );
this.trigger('classChanged');
return this;
}
})($.fn.removeClass);
Then the rest of your code would be as simple as you'd expect.
$(selector).on('classChanged', function(){ /*...*/ });
Update:
JS Fiddle Demo
This approach does make the assumption that the classes will only be changed via the jQuery addClass and removeClass methods. If classes are modified in other ways (such as direct manipulation of the class attribute through the DOM element) use of something like MutationObservers as explained in the accepted answer here would be necessary.
Also as a couple improvements to these methods:
Trigger an event for each class being added (classAdded) or removed (classRemoved) with the specific class passed as an argument to the callback function and only triggered if the particular class was actually added (not present previously) or removed (was present previously)
Only trigger classChanged if any classes are actually changed
(function( func ) {
$.fn.addClass = function(n) { // replace the existing function on $.fn
this.each(function(i) { // for each element in the collection
var $this = $(this); // 'this' is DOM element in this context
var prevClasses = this.getAttribute('class'); // note its original classes
var classNames = $.isFunction(n) ? n(i, prevClasses) : n.toString(); // retain function-type argument support
$.each(classNames.split(/\s+/), function(index, className) { // allow for multiple classes being added
if( !$this.hasClass(className) ) { // only when the class is not already present
func.call( $this, className ); // invoke the original function to add the class
$this.trigger('classAdded', className); // trigger a classAdded event
}
});
if( prevClasses != this.getAttribute('class') ) $this.trigger('classChanged'); // trigger the classChanged event
});
return this; // retain jQuery chainability
}
})($.fn.addClass); // pass the original function as an argument
(function( func ) {
$.fn.removeClass = function(n) {
this.each(function(i) {
var $this = $(this);
var prevClasses = this.getAttribute('class');
var classNames = $.isFunction(n) ? n(i, prevClasses) : n.toString();
$.each(classNames.split(/\s+/), function(index, className) {
if( $this.hasClass(className) ) {
func.call( $this, className );
$this.trigger('classRemoved', className);
}
});
if( prevClasses != this.getAttribute('class') ) $this.trigger('classChanged');
});
return this;
}
})($.fn.removeClass);
With these replacement functions you can then handle any class changed via classChanged or specific classes being added or removed by checking the argument to the callback function:
$(document).on('classAdded', '#myElement', function(event, className) {
if(className == "something") { /* do something */ }
});
Use trigger to fire your own event. When ever you change class add trigger with name
JS Fiddle DEMO
$("#main").on('click', function () {
$("#chld").addClass("bgcolorRed").trigger("cssFontSet");
});
$('#chld').on('cssFontSet', function () {
alert("Red bg set ");
});
you can use something like this:
$(this).addClass('someClass');
$(Selector).trigger('ClassChanged')
$(otherSelector).bind('ClassChanged', data, function(){//stuff });
but otherwise, no, there's no predefined function to fire an event when a class changes.
Read more about triggers here
In one of our projects we load slides into our webpage with use of AJAX. After the slides are loaded I want jQuery to execute a plugin on all new injected elements automatically.
This is the code I found else where but it didn't do the trick. Also I've tried to replace .on function with the .bind function but then the whole site died and JavaScript crashes with an overflow.
function loaded(selector, callback) {
//trigger after page load.
jQuery(function () {
callback(jQuery(selector));
});
//trigger after page update eg ajax event or jquery insert.
jQuery("body").on('DOMNodeInserted', selector, function (e) {
callback(jQuery(this));
});
}
I got the problem reproduced in a JSFiddle.
A. Wolff,
Thanks your answer solves my problem. I have edited the loaded function to the following:
function loaded(selector, callback) {
//trigger after page load.
jQuery(function () {
callback(jQuery(selector));
});
var parentSelector = "* > " + selector;
//trigger after page update eg ajax event or jquery insert.
jQuery(document).on('DOMNodeInserted', parentSelector, function (e) {
callback(jQuery(this).find(selector));
});
}
Also I've forked a new working JSFiddle project for anyone who wants a full working example.
https://jsfiddle.net/9t8cahqv/
Thanks,
Jop
Event is fired on container DIV level so your selector isn't matching. You could use instead:
loaded(":has([title])", function(element) {
element.tooltip();
});
/**/
jQuery(document).on('DOMNodeInserted', selector, function(e) {
callback(jQuery(this).find('[title]'));
});
-jsFiddle-
Another way of doing this might be, watch for a DOM
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
if (!mutation.addedNodes) return
for (var i = 0; i < mutation.addedNodes.length; i++) {
// do things to your newly added nodes here
var node = mutation.addedNodes[i]
if ($(node).hasClass("some class")) {
$(node).remove()
}
//or with id
if ($(node).attr("id") == "someId") {
$(node).remove()
}
//or any other selector
}
})
})
observer.observe(document.body, {
childList: true,
subtree: true,
attributes: false,
characterData: false
})
To Stop Observe, use
observer.disconnect();
I have jQuery replaceWith call, and I want to pop up an alert only when the replaceWith finishes loading.
To achieve this I have this very naive javascript implementation:
$(document).ready(function (){
$("#myDiv").click(function () {
$("#myDiv").replaceWith("<div>Hello World!!!</div>");
alert("done");
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="myDiv">Hello!</div>
The problem is that in this case the alert will pop-up independently of the time that the replaceWith takes. If it is fast, no problem, but if the replaceWith takes several seconds to load (which is the real case) then the pop-up appears way before, and I want to avoid that.
How can I achieve the behaviour I am looking for?
Try
$(document).ready(function() {
var body = $("body");
$("#myDiv").click(function(e) {
var html = $("<div>Hello World!!!</div>");
$("#myDiv").replaceWith(html)
.promise().done(function(elem) {
if (body.find(html).is("*")
&& !body.find(elem).is("*")) {
alert("done");
}
});
});
});
$(document).ready(function() {
var body = $("body");
$("#myDiv").click(function(e) {
var html = $("<img src=http://lorempixel.com/output/cats-q-c-1920-1920-2.jpg />");
// $("<div>Hello World!!!</div>");
$("#myDiv").replaceWith(html)
.promise().done(function(elem) {
if (body.find(html).is("*")
&& !body.find(elem).is("*")) {
alert("done");
}
});
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="myDiv">Hello!</div>
I would try getting the value of what you're replacing - then check if it exists after the replacement - then you can alert its complete.
fiddle:
http://jsfiddle.net/eavxkc3f/
jquery:
$(document).ready(function (){
$(".myDiv").click(function () {
var currentItem = $(".myDiv").html();
var replacer = "<div>Hello World!!!</div>";
$(".myDiv").replaceWith("<div>Hello World!!!</div>");
if($(".myDiv").html != currentItem){
alert("Done.");
}
});
});
Take a look at the DOM MutationObserver spec, I think it does what you want. Register it on a target node, and it will watch for changes beneath that target.
It's an updated version of the now deprecated Mutation events
A blog post with additional good info (and where I found this sample code)
Working example in this fiddle (code below)
$(document).ready(function (){
$("#myDiv").click(function () {
$("#myDiv").replaceWith("<div>Hello World!!!</div>");
});
});
// select the target node
var target = document.querySelector('#divParent');
// create an observer instance
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
//console.log(mutation.type);
alert('Done');
});
});
// configuration of the observer:
var config = { attributes: true, childList: true, characterData: true };
// pass in the target node, as well as the observer options
observer.observe(target, config);
// later, you can stop observing
//observer.disconnect();
I would like to have something like:
$('#myDiv').bind('class "submission ok" added'){
alert('class "submission ok" has been added');
});
There is no event raised when a class changes. The alternative is to manually raise an event when you programatically change the class:
$someElement.on('event', function() {
$('#myDiv').addClass('submission-ok').trigger('classChange');
});
// in another js file, far, far away
$('#myDiv').on('classChange', function() {
// do stuff
});
UPDATE - 2015
This question seems to be gathering some visitors, so here is an update with an approach which can be used without having to modify existing code using the new MutationObserver:
var $div = $("#foo");
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
var attributeValue = $(mutation.target).prop(mutation.attributeName);
console.log("Class attribute changed to:", attributeValue);
});
});
observer.observe($div[0], {
attributes: true,
attributeFilter: ['class']
});
$div.addClass('red');
.red {
color: #C00;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<div id="foo" class="bar">#foo.bar</div>
Be aware that the MutationObserver is only available for newer browsers, specifically Chrome 26, FF 14, IE 11, Opera 15 and Safari 6. See MDN for more details. If you need to support legacy browsers then you will need to use the method I outlined in my first example.
UPDATE - 2022
Here's an implementation of the above wrapped in to a jQuery extension method:
// extension method:
$.fn.classChange = function(cb) {
return $(this).each((_, el) => {
new MutationObserver(mutations => {
mutations.forEach(mutation => cb && cb(mutation.target, $(mutation.target).prop(mutation.attributeName)));
}).observe(el, {
attributes: true,
attributeFilter: ['class'] // only listen for class attribute changes
});
});
}
// usage:
const $foo = $("#foo").classChange((el, newClass) => console.log(`#${el.id} had its class updated to: ${newClass}`));
const $fizz = $("#fizz").classChange((el, newClass) => console.log(`#${el.id} had its class updated to: ${newClass}`));
// trigger
$('#trigger').on('click', () => {
$foo.removeClass('red');
$fizz.addClass('green dark-bg');
});
.red {
color: #C00;
}
.green {
color: #0C0;
}
.dark-bg {
background-color: #666;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<button id="trigger">Change classes</button>
<div id="foo" class="bar red">#foo.bar</div>
<div id="fizz" class="buzz">#fizz.buzz</div>
You could replace the original jQuery addClass and removeClass functions with your own that would call the original functions and then trigger a custom event. (Using a self-invoking anonymous function to contain the original function reference)
(function( func ) {
$.fn.addClass = function() { // replace the existing function on $.fn
func.apply( this, arguments ); // invoke the original function
this.trigger('classChanged'); // trigger the custom event
return this; // retain jQuery chainability
}
})($.fn.addClass); // pass the original function as an argument
(function( func ) {
$.fn.removeClass = function() {
func.apply( this, arguments );
this.trigger('classChanged');
return this;
}
})($.fn.removeClass);
Then the rest of your code would be as simple as you'd expect.
$(selector).on('classChanged', function(){ /*...*/ });
Update:
JS Fiddle Demo
This approach does make the assumption that the classes will only be changed via the jQuery addClass and removeClass methods. If classes are modified in other ways (such as direct manipulation of the class attribute through the DOM element) use of something like MutationObservers as explained in the accepted answer here would be necessary.
Also as a couple improvements to these methods:
Trigger an event for each class being added (classAdded) or removed (classRemoved) with the specific class passed as an argument to the callback function and only triggered if the particular class was actually added (not present previously) or removed (was present previously)
Only trigger classChanged if any classes are actually changed
(function( func ) {
$.fn.addClass = function(n) { // replace the existing function on $.fn
this.each(function(i) { // for each element in the collection
var $this = $(this); // 'this' is DOM element in this context
var prevClasses = this.getAttribute('class'); // note its original classes
var classNames = $.isFunction(n) ? n(i, prevClasses) : n.toString(); // retain function-type argument support
$.each(classNames.split(/\s+/), function(index, className) { // allow for multiple classes being added
if( !$this.hasClass(className) ) { // only when the class is not already present
func.call( $this, className ); // invoke the original function to add the class
$this.trigger('classAdded', className); // trigger a classAdded event
}
});
if( prevClasses != this.getAttribute('class') ) $this.trigger('classChanged'); // trigger the classChanged event
});
return this; // retain jQuery chainability
}
})($.fn.addClass); // pass the original function as an argument
(function( func ) {
$.fn.removeClass = function(n) {
this.each(function(i) {
var $this = $(this);
var prevClasses = this.getAttribute('class');
var classNames = $.isFunction(n) ? n(i, prevClasses) : n.toString();
$.each(classNames.split(/\s+/), function(index, className) {
if( $this.hasClass(className) ) {
func.call( $this, className );
$this.trigger('classRemoved', className);
}
});
if( prevClasses != this.getAttribute('class') ) $this.trigger('classChanged');
});
return this;
}
})($.fn.removeClass);
With these replacement functions you can then handle any class changed via classChanged or specific classes being added or removed by checking the argument to the callback function:
$(document).on('classAdded', '#myElement', function(event, className) {
if(className == "something") { /* do something */ }
});
Use trigger to fire your own event. When ever you change class add trigger with name
JS Fiddle DEMO
$("#main").on('click', function () {
$("#chld").addClass("bgcolorRed").trigger("cssFontSet");
});
$('#chld').on('cssFontSet', function () {
alert("Red bg set ");
});
you can use something like this:
$(this).addClass('someClass');
$(Selector).trigger('ClassChanged')
$(otherSelector).bind('ClassChanged', data, function(){//stuff });
but otherwise, no, there's no predefined function to fire an event when a class changes.
Read more about triggers here
I've written this code for a friend. The idea is he can add a "default" class to his textboxes, so that the default value will be grayed out, and then when he clicks it, it'll disappear, the text will return to its normal color, and then clicking a second time won't clear it:
$(document).ready(function() {
var textbox_click_handler = function clear_textbox() {
$(this).removeClass('default');
$(this).attr('value', '');
$(this).unbind(textbox_click_handler);
};
$(".default").mouseup(textbox_click_handler);
});
The clicking-to-clear works, but I get the following error:
Uncaught TypeError: Object function clear_textbox() { ... } has no method 'split'
what is causing this? How can I fix it? I would just add an anonymous function in the mouseup event, but I'm not sure how I would then unbind it -- I could just unbind everything, but I don't know if he'll want to add more functionality to it (probably not, but hey, he might want a little popup message to appear when certain textboxes are clicked, or something).
How can I fix it? What is the 'split' method for? I'm guessing it has to do with the unbind function, since the clearing works, but clicking a second time still clears it.
You can do it like this:
var textbox_click_handler = function(e) {
$(this).removeClass('default')
.attr('value', '')
.unbind(e.type, arguments.callee);
};
$(function() {
$(".default").mouseup(textbox_click_handler);
});
Or use the .one function instead that automatically unbinds the event:
$(function() {
$(".default").one('mouseup', function() {
$(this).removeClass('default').attr('value', '');
});
});
The unbind needs an event handler while you are specifying a function to its argument thereby giving you the error.
I am not sure if this is really different but try assigning the function to a variable:
var c = function clear_textbox() {
$(this).removeClass('default');
$(this).attr('value', '');
$(this).unbind('mouseup');
}
and then:
$(".default").mouseup(function(){
c();
});
if you don't want to completely unbind mouseup, check for the current state using hasClass(). No need to unbind anything.
$(document).ready(function() {
$('.default').bind('mouseup', function(e) {
var tb = $(this);
if(tb.hasClass('default')) {
tb.removeClass('default').val('');
}
});
});
Make sure you are unbinding mouseup:
function clear_textbox() {
$(this).removeClass('default');
$(this).attr('value', '');
$(this).unbind('mouseup');
}
$(function() {
$('.default').mouseup(clear_textbox);
});
Also I would write this as a plugin form:
(function($) {
$.fn.watermark = function(settings) {
this.each(function() {
$(this).css('color', 'gray');
$(this).mouseup(function() {
var $this = $(this);
$this.attr('value', '');
$this.unbind('mouseup');
});
});
return this;
};
})(jQuery);
so that your friend can simply:
$(function() {
$('.someClassYourFriendUses').watermark();
});