I needed to create a simple memory game for a course I'm attending and I came up with this:
Simple memory game
$(document).ready(function(){
// Set initial time to 0
var currentTime = 0;
// Set initial score to 0
var score = 0;
// Set initial attempt to 0
var attempts = 0;
// Placeholder
var timeHolder;
// Start the game when clicking the button #start
$('#start').on('click', init);
// Check if user hasn't clicked #start button yet
$('.board_cell').on('click.initialCheck', checkInitial);
function init() {
// Shuffle elements at beginning
shuffle();
// Handle click event and check if elements match
$('.board_cell').on('click', checkAccuracy).off('click.initialCheck');
$('#start').off('click', init);
$('#reset').on('click', reset);
// stop timer
clearInterval(timeHolder)
// Timer function will be called every 100ms
timeHolder = window.setInterval(timer, 100);
}
/*
* Main function to handle click events and do actions
* #checkAccuracy
*/
function checkAccuracy() {
var self = $(this),
allElements = $('.board_cell'),
// Url of background-image
bgUrl = self.children('.back').css('background-image'),
// Get relevant part (the image name) from the url
elementType = bgUrl.slice(bgUrl.lastIndexOf('/') + 1, bgUrl.lastIndexOf('.'));
// Flip the clicked element
self.addClass('flipped ' + elementType);
// Check if clicked element is already visible
if (self.hasClass('success')) {
showMessage('Das ist schon aufgedeckt ;)');
// Abort function by returning false
return false;
}
if($('.flipped').length >= 2) {
// Prevent clicking on other elements when 2 elements are already visible
allElements.off('click');
// Increase attempts
attempts++;
setAttempts();
}
if($('.'+elementType).length == 2) {
// If the same are visible
score++;
setScore();
showMessage(['That was a right one!!!', 'Now you got it!', 'Terrific!']);
toggleClasses('success', function(){
// Callback when toggleClasses has finsihed
if($('.success').length == allElements.length){
// If alle elements are visible
showMessage('Everything exposed, congrats!');
$('#overlay').fadeIn();
// Kill interval to prevent further increasing
clearInterval(timeHolder);
}
});
} else {
// If they are not the same
if($('.flipped').length == 2) {
toggleClasses();
showMessage(['Uhh that was wrong...', 'Are you drunk?', 'Try it again...', 'You better stop playing!',
'Seems like you need to train much more...', 'Annoying?', 'C\'mon!']);
}
}
}
/*
* Function to reset the game
*/
function reset() {
// turn elements and prevent clicking
$('.board_cell').removeClass('success flipped').off('click');
// hide overlay if visible
if($('#overlay').is(':visible')) {
$('#overlay').fadeOut();
}
// stop timer
clearInterval(timeHolder)
// set time to 0
currentTime = 0;
// set attempts to 0
attempts = 0;
setAttempts();
// set score to 0
score = 0;
setScore();
// hide message
showMessage('');
// set visible time to 0
$('#time span').text(currentTime);
// Check if user has clicked #start button
$('.board_cell').on('click.initialCheck', checkInitial);
$('#start').on('click', init);
}
/*
* Function to show a message
*/
function showMessage(msg) {
if(typeof msg == 'object') {
var randomNumber = Math.floor((Math.random()*msg.length)+1);
msg = msg[randomNumber-1];
}
$('#message span').html(msg);
}
/*
* Function to toggleClasses on clickable elements
*/
function toggleClasses(extraClass, callback) {
setTimeout(function(){
$('.flipped').removeClass().addClass('board_cell '+extraClass);
$('.board_cell').on('click', checkAccuracy);
if(typeof callback != 'undefined') {
callback();
}
}, 1000);
}
/*
* Function to increase score
*/
function setScore() {
$('#score span').text(score);
}
/*
* Function to increase attempts
*/
function setAttempts() {
$('#attempts span').text(attempts);
}
/*
* Function for timer
*/
function timer() {
currentTime = currentTime + 1;
$('#time span').text(currentTime/10);
}
/*
* Function for showing message when user hasn't clicked #start button yet
*/
function checkInitial() {
showMessage('You need to press the "Start Game" button to beginn');
}
/*
* Function for shuffling elements
*/
function shuffle() {
var elementsArray = [];
$('.back').each(function(index){
elementsArray.push($(this).css('background-image'))
});
elementsArray.sort(function() {return 0.5 - Math.random()})
$('.back').each(function(index){
$(this).css('background-image', elementsArray[index]);
});
}
});
The hidden images are added through inline styling with background-image and are shuffled on each start/reset but that doesn't prevent a user to cheat during the game (looking at the source code tells the solution immediately).
I'd like to know if there is a way to hide the background-image value in the source code?
I tried some base64 encryption but as the browser interprets this immediately it doesn't serve at all. Another idea I had was to encrypt the background-image with php, display a random output (which was saved in a database for instance) in the markup and communicate through ajax requests with the php file on each click event. I'm not sure if this works, but anyway it seems like a circuitous way of handling it..
Any suggestion on how to solve this in safe and efficient way?
A safe (and overkill) solution would be to do this entirely serverside. Start a new game by generating a random session id and shuffling the squares. Then, your clientside JS requests the square images through AJAX via some sort of API:
GET /<session_id>/square/<x>/<y>
Once you rate limit the requests serverside to prevent a user from downloading all of the images at once, your game is safe.
So I currently use something like:
$(window).resize(function(){resizedw();});
But this gets called many times while resizing process goes on. Is it possible to catch an event when it ends?
You can use setTimeout() and clearTimeout()
function resizedw(){
// Haven't resized in 100ms!
}
var doit;
window.onresize = function(){
clearTimeout(doit);
doit = setTimeout(resizedw, 100);
};
Code example on jsfiddle.
I had luck with the following recommendation: http://forum.jquery.com/topic/the-resizeend-event
Here's the code so you don't have to dig through his post's link & source:
var rtime;
var timeout = false;
var delta = 200;
$(window).resize(function() {
rtime = new Date();
if (timeout === false) {
timeout = true;
setTimeout(resizeend, delta);
}
});
function resizeend() {
if (new Date() - rtime < delta) {
setTimeout(resizeend, delta);
} else {
timeout = false;
alert('Done resizing');
}
}
Thanks sime.vidas for the code!
This is the code that I write according to #Mark Coleman answer:
$(window).resize(function() {
clearTimeout(window.resizedFinished);
window.resizedFinished = setTimeout(function(){
console.log('Resized finished.');
}, 250);
});
Thanks Mark!
Internet Explorer provides a resizeEnd event. Other browsers will trigger the resize event many times while you're resizing.
There are other great answers here that show how to use setTimeout and the .throttle, .debounce methods from lodash and underscore, so I will mention Ben Alman's throttle-debounce jQuery plugin which accomplishes what you're after.
Suppose you have this function that you want to trigger after a resize:
function onResize() {
console.log("Resize just happened!");
};
Throttle Example
In the following example, onResize() will only be called once every 250 milliseconds during a window resize.
$(window).resize( $.throttle( 250, onResize) );
Debounce Example
In the following example, onResize() will only be called once at the end of a window resizing action. This achieves the same result that #Mark presents in his answer.
$(window).resize( $.debounce( 250, onResize) );
There is an elegant solution using the Underscore.js So, if you are using it in your project you can do the following -
$( window ).resize( _.debounce( resizedw, 500 ) );
This should be enough :) But, If you are interested to read more on that, you can check my blog post - http://rifatnabi.com/post/detect-end-of-jquery-resize-event-using-underscore-debounce(deadlink)
There is a much simpler method to execute a function at the end of the resize than calculate the delta time between two calls, simply do it like this :
var resizeId;
$(window).resize(function() {
clearTimeout(resizeId);
resizeId = setTimeout(resizedEnded, 500);
});
function resizedEnded(){
...
}
And the equivalent for Angular2 :
private resizeId;
#HostListener('window:resize', ['$event'])
onResized(event: Event) {
clearTimeout(this.resizeId);
this.resizeId = setTimeout(() => {
// Your callback method here.
}, 500);
}
For the angular method, use the () => { } notation in the setTimeout to preserve the scope, otherwise you will not be able to make any function calls or use this.
One solution is extend jQuery with a function, e.g.: resized
$.fn.resized = function (callback, timeout) {
$(this).resize(function () {
var $this = $(this);
if ($this.data('resizeTimeout')) {
clearTimeout($this.data('resizeTimeout'));
}
$this.data('resizeTimeout', setTimeout(callback, timeout));
});
};
Sample usage:
$(window).resized(myHandler, 300);
You can store a reference id to any setInterval or setTimeout. Like this:
var loop = setInterval(func, 30);
// some time later clear the interval
clearInterval(loop);
To do this without a "global" variable you can add a local variable to the function itself. Ex:
$(window).resize(function() {
clearTimeout(this.id);
this.id = setTimeout(doneResizing, 500);
});
function doneResizing(){
$("body").append("<br/>done!");
}
You can use setTimeout() and clearTimeout() in conjunction with jQuery.data:
$(window).resize(function() {
clearTimeout($.data(this, 'resizeTimer'));
$.data(this, 'resizeTimer', setTimeout(function() {
//do something
alert("Haven't resized in 200ms!");
}, 200));
});
Update
I wrote an extension to enhance jQuery's default on (& bind)-event-handler. It attaches an event handler function for one or more events to the selected elements if the event was not triggered for a given interval. This is useful if you want to fire a callback only after a delay, like the resize event, or else.
https://github.com/yckart/jquery.unevent.js
;(function ($) {
var methods = { on: $.fn.on, bind: $.fn.bind };
$.each(methods, function(k){
$.fn[k] = function () {
var args = [].slice.call(arguments),
delay = args.pop(),
fn = args.pop(),
timer;
args.push(function () {
var self = this,
arg = arguments;
clearTimeout(timer);
timer = setTimeout(function(){
fn.apply(self, [].slice.call(arg));
}, delay);
});
return methods[k].apply(this, isNaN(delay) ? arguments : args);
};
});
}(jQuery));
Use it like any other on or bind-event handler, except that you can pass an extra parameter as a last:
$(window).on('resize', function(e) {
console.log(e.type + '-event was 200ms not triggered');
}, 200);
http://jsfiddle.net/ARTsinn/EqqHx/
Mark Coleman's answer is certainly far better than the selected answer, but if you want to avoid the global variable for the timeout ID (the doit variable in Mark's answer), you could do one of the following:
(1) Use a an immediately invoked function expression (IIFE) to create a closure.
$(window).resize((function() { // This function is immediately invoked
// and returns the closure function.
var timeoutId;
return function() {
clearTimeout(timeoutId);
timeoutId = setTimeout(function() {
timeoutId = null; // You could leave this line out.
// Code to execute on resize goes here.
}, 100);
};
})());
(2) Use a property of the event handler function.
$(window).resize(function() {
var thisFunction = arguments.callee;
clearTimeout(thisFunction.timeoutId);
thisFunction.timeoutId = setTimeout(function() {
thisFunction.timeoutId = null; // You could leave this line out.
// Code to execute on resize goes here.
}, 100);
});
This is what I use for delaying repeated actions, it can be called in multiple places in your code:
function debounce(func, wait, immediate) {
var timeout;
return function() {
var context = this, args = arguments;
var later = function() {
timeout = null;
if (!immediate) func.apply(context, args);
};
var callNow = immediate && !timeout;
clearTimeout(timeout);
timeout = setTimeout(later, wait);
if (callNow) func.apply(context, args);
};
};
Usage:
$(window).resize(function () {
debounce(function() {
//...
}, 500);
});
ResizeStart and ResizeEnd events for window
http://jsfiddle.net/04fLy8t4/
I implemented a function which trigs two events on the user DOM element:
resizestart
resizeend
Code:
var resizeEventsTrigger = (function () {
function triggerResizeStart($el) {
$el.trigger('resizestart');
isStart = !isStart;
}
function triggerResizeEnd($el) {
clearTimeout(timeoutId);
timeoutId = setTimeout(function () {
$el.trigger('resizeend');
isStart = !isStart;
}, delay);
}
var isStart = true;
var delay = 200;
var timeoutId;
return function ($el) {
isStart ? triggerResizeStart($el) : triggerResizeEnd($el);
};
})();
$("#my").on('resizestart', function () {
console.log('resize start');
});
$("#my").on('resizeend', function () {
console.log('resize end');
});
window.onresize = function () {
resizeEventsTrigger( $("#my") );
};
This is a modification to Dolan's code above, I've added a feature which checks the window size at the start of the resize and compares it to the size at the end of the resize, if size is either bigger or smaller than the margin (eg. 1000) then it reloads.
var rtime = new Date(1, 1, 2000, 12,00,00);
var timeout = false;
var delta = 200;
var windowsize = $window.width();
var windowsizeInitial = $window.width();
$(window).on('resize',function() {
windowsize = $window.width();
rtime = new Date();
if (timeout === false) {
timeout = true;
setTimeout(resizeend, delta);
}
});
function resizeend() {
if (new Date() - rtime < delta) {
setTimeout(resizeend, delta);
return false;
} else {
if (windowsizeInitial > 1000 && windowsize > 1000 ) {
setTimeout(resizeend, delta);
return false;
}
if (windowsizeInitial < 1001 && windowsize < 1001 ) {
setTimeout(resizeend, delta);
return false;
} else {
timeout = false;
location.reload();
}
}
windowsizeInitial = $window.width();
return false;
}
Here is VERY simple script to trigger both a 'resizestart' and 'resizeend' event on the window object.
There is no need to muck around with dates and times.
The d variable represents the number of milliseconds between resize events before triggering the resize end event, you can play with this to change how sensitive the end event is.
To listen to these events all you need to do is:
resizestart: $(window).on('resizestart', function(event){console.log('Resize Start!');});
resizeend:
$(window).on('resizeend', function(event){console.log('Resize End!');});
(function ($) {
var d = 250, t = null, e = null, h, r = false;
h = function () {
r = false;
$(window).trigger('resizeend', e);
};
$(window).on('resize', function (event) {
e = event || e;
clearTimeout(t);
if (!r) {
$(window).trigger('resizestart', e);
r = true;
}
t = setTimeout(h, d);
});
}(jQuery));
i wrote a litte wrapper function on my own...
onResize = function(fn) {
if(!fn || typeof fn != 'function')
return 0;
var args = Array.prototype.slice.call(arguments, 1);
onResize.fnArr = onResize.fnArr || [];
onResize.fnArr.push([fn, args]);
onResize.loop = function() {
$.each(onResize.fnArr, function(index, fnWithArgs) {
fnWithArgs[0].apply(undefined, fnWithArgs[1]);
});
};
$(window).on('resize', function(e) {
window.clearTimeout(onResize.timeout);
onResize.timeout = window.setTimeout("onResize.loop();", 300);
});
};
Here is the usage:
var testFn = function(arg1, arg2) {
console.log('[testFn] arg1: '+arg1);
console.log('[testFn] arg2: '+arg2);
};
// document ready
$(function() {
onResize(testFn, 'argument1', 'argument2');
});
(function(){
var special = jQuery.event.special,
uid1 = 'D' + (+new Date()),
uid2 = 'D' + (+new Date() + 1);
special.resizestart = {
setup: function() {
var timer,
handler = function(evt) {
var _self = this,
_args = arguments;
if (timer) {
clearTimeout(timer);
} else {
evt.type = 'resizestart';
jQuery.event.handle.apply(_self, _args);
}
timer = setTimeout( function(){
timer = null;
}, special.resizestop.latency);
};
jQuery(this).bind('resize', handler).data(uid1, handler);
},
teardown: function(){
jQuery(this).unbind( 'resize', jQuery(this).data(uid1) );
}
};
special.resizestop = {
latency: 200,
setup: function() {
var timer,
handler = function(evt) {
var _self = this,
_args = arguments;
if (timer) {
clearTimeout(timer);
}
timer = setTimeout( function(){
timer = null;
evt.type = 'resizestop';
jQuery.event.handle.apply(_self, _args);
}, special.resizestop.latency);
};
jQuery(this).bind('resize', handler).data(uid2, handler);
},
teardown: function() {
jQuery(this).unbind( 'resize', jQuery(this).data(uid2) );
}
};
})();
$(window).bind('resizestop',function(){
//...
});
Well, as far as the window manager is concerned, each resize event is its own message, with a distinct beginning and end, so technically, every time the window is resized, it is the end.
Having said that, maybe you want to set a delay to your continuation? Here's an example.
var t = -1;
function doResize()
{
document.write('resize');
}
$(document).ready(function(){
$(window).resize(function(){
clearTimeout(t);
t = setTimeout(doResize, 1000);
});
});
I guess my case might be different from some others but I had a problem only with orientation change on iOS but wanted the resize event to run immediately. I used the ScreenOrientation API:
screen.orientation.addEventListener('change', (e) => {});
I took a slightly different tack and relied on mouseUp as the end of the resize event. trackSize is called on documentReady and the initial value of wide is set then, too.
var THRESHOLD = 784;
var TALL = 125, SHORT = 50;
var wide = (window.document.body.clientWidth >= THRESHOLD );
function trackSize() {
if( !wide ) {
setHeight( TALL );
} else {
setHeight( SHORT );
}
parent.window.addEventListener('resize', onResize);
}
function onResize(e) {
parent.window.removeEventListener('resize', onResize);
parent.window.addEventListener('mouseup', onMouseUp) ;
}
function onMouseUp(e) {
parent.window.removeEventListener('mouseup', onMouseUp);
wide = (window.document.body.clientWidth >= THRESHOLD);
trackSize();
}
After having set our window's initial height, we begin listening for a resize event. When it starts, we stop listening and start listening for the mouseUp event. Thus, we know that mouseUp will end the resizing. In mouseUp, we stop listening and set a toggle based on the window's width, then loop back to trackSize.
trackSize starts by setting the window's height based on the toggle -- if below the threshold, we increase height (because Bootstrap columns stack at small widths), otherwise set to standard. And then we listen again for the next resize event.
CAVEAT: This solution doesn't really work for resizing instantly using the maximize or restore window buttons. Maybe adding a test like isMouseDown and bypassing the mouse listener would suffice - I haven't yet tested that.
since the selected answer didn't actually work .. and if you're not using jquery here is a simple throttle function with an example of how to use it with window resizing
function throttle(end,delta) {
var base = this;
base.wait = false;
base.delta = 200;
base.end = end;
base.trigger = function(context) {
//only allow if we aren't waiting for another event
if ( !base.wait ) {
//signal we already have a resize event
base.wait = true;
//if we are trying to resize and we
setTimeout(function() {
//call the end function
if(base.end) base.end.call(context);
//reset the resize trigger
base.wait = false;
}, base.delta);
}
}
};
var windowResize = new throttle(function() {console.log('throttle resize');},200);
window.onresize = function(event) {
windowResize.trigger();
}
this worked for me as I did not want to use any plugins.
$(window).resize(function() {
var originalWindowSize = 0;
var currentWidth = 0;
var setFn = function () {
originalWindowSize = $(window).width();
};
var checkFn = function () {
setTimeout(function () {
currentWidth = $(window).width();
if (currentWidth === originalWindowSize) {
console.info("same? = yes")
// execute code
} else {
console.info("same? = no");
// do nothing
}
}, 500)
};
setFn();
checkFn();
});
On window re-size invoke "setFn" which gets width of window and save as "originalWindowSize". Then invoke "checkFn" which after 500ms (or your preference) gets the current window size, and compares the original to the current, if they are not the same, then the window is still being re-sized. Don't forget to remove console messages in production, and (optional) can make "setFn" self executing.
var resizeTimer;
$( window ).resize(function() {
if(resizeTimer){
clearTimeout(resizeTimer);
}
resizeTimer = setTimeout(function() {
//your code here
resizeTimer = null;
}, 200);
});
This worked for what I was trying to do in chrome. This won't fire the callback until 200ms after last resize event.
UPDATE!
Better alternative also created by me is here:
https://stackoverflow.com/a/23692008/2829600
(supports "delete functions")
ORIGINAL POST:
I wrote this simple function for handling delay in execution, useful inside jQuery .scroll() and .resize() So callback_f will run only once for specific id string.
function delay_exec( id, wait_time, callback_f ){
// IF WAIT TIME IS NOT ENTERED IN FUNCTION CALL,
// SET IT TO DEFAULT VALUE: 0.5 SECOND
if( typeof wait_time === "undefined" )
wait_time = 500;
// CREATE GLOBAL ARRAY(IF ITS NOT ALREADY CREATED)
// WHERE WE STORE CURRENTLY RUNNING setTimeout() FUNCTION FOR THIS ID
if( typeof window['delay_exec'] === "undefined" )
window['delay_exec'] = [];
// RESET CURRENTLY RUNNING setTimeout() FUNCTION FOR THIS ID,
// SO IN THAT WAY WE ARE SURE THAT callback_f WILL RUN ONLY ONE TIME
// ( ON LATEST CALL ON delay_exec FUNCTION WITH SAME ID )
if( typeof window['delay_exec'][id] !== "undefined" )
clearTimeout( window['delay_exec'][id] );
// SET NEW TIMEOUT AND EXECUTE callback_f WHEN wait_time EXPIRES,
// BUT ONLY IF THERE ISNT ANY MORE FUTURE CALLS ( IN wait_time PERIOD )
// TO delay_exec FUNCTION WITH SAME ID AS CURRENT ONE
window['delay_exec'][id] = setTimeout( callback_f , wait_time );
}
// USAGE
jQuery(window).resize(function() {
delay_exec('test1', 1000, function(){
console.log('1st call to delay "test1" successfully executed!');
});
delay_exec('test1', 1000, function(){
console.log('2nd call to delay "test1" successfully executed!');
});
delay_exec('test1', 1000, function(){
console.log('3rd call to delay "test1" successfully executed!');
});
delay_exec('test2', 1000, function(){
console.log('1st call to delay "test2" successfully executed!');
});
delay_exec('test3', 1000, function(){
console.log('1st call to delay "test3" successfully executed!');
});
});
/* RESULT
3rd call to delay "test1" successfully executed!
1st call to delay "test2" successfully executed!
1st call to delay "test3" successfully executed!
*/
var flag=true;
var timeloop;
$(window).resize(function(){
rtime=new Date();
if(flag){
flag=false;
timeloop=setInterval(function(){
if(new Date()-rtime>100)
myAction();
},100);
}
})
function myAction(){
clearInterval(timeloop);
flag=true;
//any other code...
}
I don't know is my code work for other but it's really do a great job for me. I got this idea by analyzing Dolan Antenucci code because his version is not work for me and I really hope it'll be helpful to someone.
var tranStatus = false;
$(window).resizeend(200, function(){
$(".cat-name, .category").removeAttr("style");
//clearTimeout(homeResize);
$("*").one("webkitTransitionEnd otransitionend oTransitionEnd msTransitionEnd transitionend",function(event) {
tranStatus = true;
});
processResize();
});
function processResize(){
homeResize = setInterval(function(){
if(tranStatus===false){
console.log("not yet");
$("*").one("webkitTransitionEnd otransitionend oTransitionEnd msTransitionEnd transitionend",function(event) {
tranStatus = true;
});
}else{
text_height();
clearInterval(homeResize);
}
},200);
}
I wrote a function that passes a function when wrapped in any resize event. It uses an interval so that the resize even isn't constantly creating timeout events. This allows it to perform independently of the resize event other than a log entry that should be removed in production.
https://github.com/UniWrighte/resizeOnEnd/blob/master/resizeOnEnd.js
$(window).resize(function(){
//call to resizeEnd function to execute function on resize end.
//can be passed as function name or anonymous function
resizeEnd(function(){
});
});
//global variables for reference outside of interval
var interval = null;
var width = $(window).width();
var numi = 0; //can be removed in production
function resizeEnd(functionCall){
//check for null interval
if(!interval){
//set to new interval
interval = setInterval(function(){
//get width to compare
width2 = $(window).width();
//if stored width equals new width
if(width === width2){
//clear interval, set to null, and call passed function
clearInterval(interval);
interval = null; //precaution
functionCall();
}
//set width to compare on next interval after half a second
width = $(window).width();
}, 500);
}else{
//logging that should be removed in production
console.log("function call " + numi++ + " and inteval set skipped");
}
}
I'd like to set something up on my site where when you scroll within 15% of the bottom of the page an element flyouts from the side... I'm not sure how to get started here... should I add a listener for a scroll function or something?
I'm trying to recreate the effect at the bottom of this page: http://www.nytimes.com/2011/01/25/world/europe/25moscow.html?_r=1
update
I have this code....
console.log(document.body.scrollTop); //shows 0
console.log(document.body.scrollHeight * 0.85); //shows 1038.7
if (document.body.scrollTop > document.body.scrollHeight * 0.85) {
console.log();
$('#flyout').animate({
right: '0'
},
5000,
function() {
});
}
the console.log() values aren't changing when I scroll to the bottom of the page. The page is twice as long as my viewport.
[Working Demo]
$(document).ready(function () {
var ROOT = (function () {
var html = document.documentElement;
var htmlScrollTop = html.scrollTop++;
var root = html.scrollTop == htmlScrollTop + 1 ? html : document.body;
html.scrollTop = htmlScrollTop;
return root;
})();
// may be recalculated on resize
var limit = (document.body.scrollHeight - $(window).height()) * 0.85;
var visible = false;
var last = +new Date;
$(window).scroll(function () {
if (+new Date - last > 30) { // more than 30 ms elapsed
if (visible && ROOT.scrollTop < limit) {
setTimeout(function () { hide(); visible = false; }, 1);
} else if (!visible && ROOT.scrollTop > limit) {
setTimeout(function () { show(); visible = true; }, 1);
}
last = +new Date;
}
});
});
I know this is an old topic, but the above code that received the check mark was also triggering the $(window).scroll() event listener too many times.
I guess twitter had this same issue at one point. John Resig blogged about it here: http://ejohn.org/blog/learning-from-twitter/
$(document).ready(function(){
var ROOT = (function () {
var html = document.documentElement;
var htmlScrollTop = html.scrollTop++;
var root = html.scrollTop == htmlScrollTop + 1 ? html : document.body;
html.scrollTop = htmlScrollTop;
return root;
})();
// may be recalculated on resize
var limit = (document.body.scrollHeight - $(window).height()) * 0.85;
var visible = false;
var last = +new Date;
var didScroll = false;
$(window).scroll(function(){
didScroll = true;
})
setInterval(function(){
if(didScroll){
didScroll = false;
if (visible && ROOT.scrollTop < limit) {
hideCredit();
visible = false;
} else if (!visible && ROOT.scrollTop > limit) {
showCredit();
visible = true;
}
}
}, 30);
function hideCredit(){
console.log('The hideCredit function has been called.');
}
function showCredit(){
console.log('The showCredit function has been called.');
}
});
So the difference between the two blocks of code is when and how the timer is called. In this code the timer is called off the bat. So every 30 millaseconds, it checks to see if the page has been scrolled. if it's been scrolled, then it checks to see if we've passed the point on the page where we want to show the hidden content. Then, if that checks true, the actual function then gets called to show the content. (In my case I've just got a console.log print out in there right now.
This seems to be better to me than the other solution because the final function only gets called once per iteration. With the other solution, the final function was being called between 4 and 5 times. That's got to be saving resources. But maybe I'm missing something.
bad idea to capture the scroll event, best to use a timer and every few milliseconds check the scroll position and if in the range you need then execute the necessary code for what you need
Update: in the past few years the best practice is to subscribe to the event and use a throttle avoiding excessive processing https://lodash.com/docs#throttle
Something like this should work:
$(window).scroll(function() {
if (document.body.scrollTop > document.body.scrollHeight * 0.85) {
// flyout
}
});
document.body.scrollTop may not work equally well on all browsers (it actually depends on browser and doctype); so we need to abstract that in a function.
Also, we need to flyout only one time. So we can unbind the event handler after having flyed out.
And we don't want the flyout effect to slow down scrolling, so we will run our flytout function out of the event loop (by using setTimeout()).
Here is the final code:
// we bind the scroll event, with the 'flyout' namespace
// so we can unbind easily
$(window).bind('scroll.flyout', (function() {
// this function is defined only once
// it is private to our event handler
function getScrollTop() {
// if one of these values evaluates to false, this picks the other
return (document.documentElement.scrollTop||document.body.scrollTop);
}
// this is the actual event handler
// it has the getScrollTop() in its scope
return function() {
if (getScrollTop() > (document.body.scrollHeight-$(window).height()) * 0.85) {
// flyout
// out of the event loop
setTimeout(function() {
alert('flyout!');
}, 1);
// unbind the event handler
// so that it's not call anymore
$(this).unbind('scroll.flyout');
}
};
})());
So in the end, only getScrollTop() > document.body.scrollHeight * 0.85 is executed at each scroll event, which is acceptable.
The flyout effect is ran only one time, and after the event has returned, so it won't affect scrolling.
I'd like to do some fancy jQuery stuff when the user scrolls the page. But I have no idea how to tackle this problem, since there is only the scroll() method.
Any ideas?
You can make the scroll() have a time-out that gets overwritten each times the user scrolls. That way, when he stops after a certain amount of milliseconds your script is run, but if he scrolls in the meantime the counter will start over again and the script will wait until he is done scrolling again.
Update:
Because this question got some action again I figured I might as well update it with a jQuery extension that adds a scrollEnd event
// extension:
$.fn.scrollEnd = function(callback, timeout) {
$(this).on('scroll', function(){
var $this = $(this);
if ($this.data('scrollTimeout')) {
clearTimeout($this.data('scrollTimeout'));
}
$this.data('scrollTimeout', setTimeout(callback,timeout));
});
};
// how to call it (with a 1000ms timeout):
$(window).scrollEnd(function(){
alert('stopped scrolling');
}, 1000);
<script src="https://code.jquery.com/jquery-3.5.1.min.js" integrity="sha256-9/aliU8dGd2tb6OSsuzixeV4y/faTqgFtohetphbbj0=" crossorigin="anonymous"></script>
<div style="height: 200vh">
Long div
</div>
Here is a simple example using setTimeout to fire a function when the user stops scrolling:
(function() {
var timer;
$(window).bind('scroll',function () {
clearTimeout(timer);
timer = setTimeout( refresh , 150 );
});
var refresh = function () {
// do stuff
console.log('Stopped Scrolling');
};
})();
The timer is cleared while the scroll event is firing. Once scrolling stops, the refresh function is fired.
Or as a plugin:
$.fn.afterwards = function (event, callback, timeout) {
var self = $(this), delay = timeout || 16;
self.each(function () {
var $t = $(this);
$t.on(event, function(){
if ($t.data(event+'-timeout')) {
clearTimeout($t.data(event+'-timeout'));
}
$t.data(event + '-timeout', setTimeout(function () { callback.apply($t); },delay));
})
});
return this;
};
To fire callback after 100ms of the last scroll event on a div (with namespace):
$('div.mydiv').afterwards('scroll.mynamespace', function(e) {
// do stuff when stops scrolling
$(this).addClass('stopped');
}, 100
);
I use this for scroll and resize.
Here is another more generic solution based on the same ideas mentioned:
var delayedExec = function(after, fn) {
var timer;
return function() {
timer && clearTimeout(timer);
timer = setTimeout(fn, after);
};
};
var scrollStopper = delayedExec(500, function() {
console.log('stopped it');
});
document.getElementById('box').addEventListener('scroll', scrollStopper);
I had the need to implement onScrollEnd event discussed hear as well.
The idea of using timer works for me.
I implement this using JavaScript Module Pattern:
var WindowCustomEventsModule = (function(){
var _scrollEndTimeout = 30;
var _delayedExec = function(callback){
var timer;
return function(){
timer && clearTimeout(timer);
timer = setTimeout(callback, _scrollEndTimeout);
}
};
var onScrollEnd = function(callback) {
window.addEventListener('scroll', _delayedExec(callback), false);
};
return {
onScrollEnd: onScrollEnd
}
})();
// usage example
WindowCustomEventsModule.onScrollEnd(function(){
//
// do stuff
//
});
Hope this will help / inspire someone
Why so complicated? As the documentation points out, this http://jsfiddle.net/x3s7F/9/ works!
$('.frame').scroll(function() {
$('.back').hide().fadeIn(100);
}
http://api.jquery.com/scroll/.
Note: The scroll event on Windows Chrome is differently to all others. You need to scroll fast to get the same as result as in e.g. FF. Look at https://liebdich.biz/back.min.js the "X" function.
Some findings from my how many ms a scroll event test:
Safari, Mac FF, Mac Chrome: ~16ms an event.
Windows FF: ~19ms an event.
Windows Chrome: up to ~130ms an event, when scrolling slow.
Internet Explorer: up to ~110ms an event.
http://jsfiddle.net/TRNCFRMCN/1Lygop32/4/.
There is no such event as 'scrollEnd'. I recommend that you check the value returned by scroll() every once in a while (say, 200ms) using setInterval, and record the delta between the current and the previous value. If the delta becomes zero, you can use it as your event.
There are scrollstart and scrollstop functions that are part of jquery mobile.
Example using scrollstop:
$(document).on("scrollstop",function(){
alert("Stopped scrolling!");
});
Hope this helps someone.
The scrollEnd event is coming. It's currently experimental and is only supported by Firefox. See the Mozilla documentation here - https://developer.mozilla.org/en-US/docs/Web/API/Document/scrollend_event
Once it's supported by more browsers, you can use it like this...
document.onscrollend = (event) => {
console.log('Document scrollend event fired!');
};
I pulled some code out of a quick piece I cobbled together that does this as an example (note that scroll.chain is an object containing two arrays start and end that are containers for the callback functions). Also note that I am using jQuery and underscore here.
$('body').on('scroll', scrollCall);
scrollBind('end', callbackFunction);
scrollBind('start', callbackFunction);
var scrollCall = function(e) {
if (scroll.last === false || (Date.now() - scroll.last) <= 500) {
scroll.last = Date.now();
if (scroll.timeout !== false) {
window.clearTimeout(scroll.timeout);
} else {
_(scroll.chain.start).each(function(f){
f.call(window, {type: 'start'}, e.event);
});
}
scroll.timeout = window.setTimeout(self.scrollCall, 550, {callback: true, event: e});
return;
}
if (e.callback !== undefined) {
_(scroll.chain.end).each(function(f){
f.call(window, {type: 'end'}, e.event);
});
scroll.last = false;
scroll.timeout = false;
}
};
var scrollBind = function(type, func) {
type = type.toLowerCase();
if (_(scroll.chain).has(type)) {
if (_(scroll.chain[type]).indexOf(func) === -1) {
scroll.chain[type].push(func);
return true;
}
return false;
}
return false;
}