I have a spin function which makes the number rotates every 4 seconds. Now I need to start that function once when the numbers are on viewport, so when on viewport start function only once, I don't mean to rotate the numbers only once, just the function to start only once, and when numbers are not in the viewport anymore then do nothing and so on.
My problem comes when I play scrolling while numbers are visible, because that makes the function spin, to fire many times.
I kinda understand what is going on here, but just can't manage it in javascript, everytime I scroll, the scrolling listener fire multiple times so it also fires multiple times the .each() and also the spin function? If someone can explain what is the problem and how to solve it, would be nice.
If you have a fiddle to share would be nice.
Fiddle
var slots = $('.numbers').find('.slot');
if( slots.length ){
var isScrolling;
window.addEventListener('scroll', function ( event ) {
// Clear our timeout throughout the scroll
window.clearTimeout( isScrolling );
// Set a timeout to run after scrolling ends
isScrolling = setTimeout(function() {
slots.each(function(){
let slotHeight = $(this).height();
let animateTo = (-slotHeight + 21);
if( isElementInViewport( $(this)[0] ) ){
if( ! $(this).is(":animated") ){
spin($(this), animateTo);
}
else{
return false;
}
}
});
}, 200);
});
}
Thank you.
What you're seeing makes sense, because the scroll event triggers many, many times while scrolling (not just once when the scroll starts or ends or something like that).
If you'd like your behavior to be triggered less often, there are several options available to you. You could keep the scroll event listener and use a debounce or a throttle to reduce the number of triggers. Or you could listen to a different even altogether.
In your case, it sounds like you would like to trigger an action once an element comes into view, and then only once. For that, you could still run your scroll handler, but check if the element in question is visible, and then run the rest of your logic. Once that's done, you could de-register your event handler (scroll handlers are potentially expensive because they run so often).
Ideally in a browser, mousemove should fire every frame when the mouse keeps moving. But when a key is pressed (or repeated) or released, the mousemove stops firing for a frame or two.
We can test this with the following code:
t0 = new Date().getTime()
window.onmousemove = function() {
t = new Date().getTime()
if (t-t0 > 20)
console.log(t-t0)
t0 = t
}
Try keep your mouse moving. The console will print delay of mousemove only when you press, release a key or keep a key pressed (because it's repeated).
I have tested this on both Firefox and Chrome. I use macOS 10.14.2.
I'm writing a web action game, so I need to make sure the mouse position is updated every frame. Any solutions please?
t0 = new Date().getTime()
window.onmousemove = function() {
t = new Date().getTime()
if (t-t0 > 2)
console.log(t-t0)
t0 = t
}
this will make console.log() go crazy fast it wil not skip when you move your mouse fast , also tested your code doesn't skip when pressing keys , on Chrome , Windows10
also you should consider using a main loop for your game to handle and manage times and frames and events
Edit
I'm essentially trying to create the Mario style jump, so as you touch / mousedown on the body I have an object that starts travelling up, but when you let go this acceleration stops. This means I can't use FastClick as I'm looking for touchstart, touchend events, not a single click event.
~
I'm trying to respond to a touchstart event on mobile in browser. At the moment I'm using these two listeners:
document.body.addEventListener('touchstart', function(e) {
e.preventDefault();
space_on();
return false;
}, false);
document.body.addEventListener('touchend', function(e) {
e.preventDefault();
space_off();
return false;
}, false);
I'm essentially trying to emulate something I've had working really well where I use keydown and keyup events to make a box jump and fall respectively.
The issue I'm having is that a touch start, if you don't swipe, is actually delaying for a short while. Either that, or a calculation is making me lose framerate.
I'm already using fastclick and that isn't effecting this (probably because it was never meant to fire on touchstart listeners). You can see what I mean here:
https://www.youtube.com/watch?v=8GgjSFgtmFk
I swipe 3 times and the box jumps immediately, and then I click 3 times and you can see (especially on the second one) it loses framerate a little bit or is delayed. Here is another, possibly clearer example: https://www.youtube.com/watch?v=BAPw1M2Yfig
There is a demo here:
http://codepen.io/EightArmsHQ/live/7d851f0e1d3a274b57221dac9aebc16a/
Just please bear in mind that you'll need to either be on a phone or touch device or emulate touches in chrome.
Can anyone help me lose the framerate drop or delay that is experienced on a touchstart that doesn't turn into a swipe?
You should not write your animation loop using setInterval.
Try to replace it with requestAnimationFrame, like this:
function render() {
ctx.fillStyle = 'rgba(255,255,255,0.8)';
ctx.fillRect(0, 0, canvas.width, canvas.height);
draw_rects();
move();
fall();
move_scenery();
move_jumper();
jumper.y += jumper.vy;
requestAnimationFrame(render);
}
$(window).load(function() {
requestAnimationFrame(render);
});
Like I've done in this pen.
Now your render function is called as soon as the browser is ready to render a new frame. Note that this implementation doesn't use your fps variable, so your frame rate now depends on the browser/device speed. I tested the pen I've edited on my phone and now the animation is way smoother but the scenery is moving too fast (for me at least).
If you want a constant frame rate you can throttle it as explained, for example, here.
Note that you really don't need Fastclick because you aren't binding any click event in your code.
On virtually all current browsers (extensive details from patrickhlauke on github, which I summarised in an SO answer, and also some more info from QuirksMode), touchscreen touches trigger mouseover events (sometimes creating an invisible pseudo-cursor that stays where the user touched until they touch elsewhere).
Sometimes this causes undesirable behaviour in cases where touch/click and mouseover are intended to do different things.
From inside a function responding to a mouseover event, that has been passed the event object, is there any way I can check if this was a "real" mouseover from a moving cursor that moved from outside an element to inside it, or if it was caused by this touchscreen behaviour from a touchscreen touch?
The event object looks identical. For example, on chrome, a mouseover event caused by a user touching a touchscreen has type: "mouseover" and nothing I can see that would identify it as touch related.
I had the idea of binding an event to touchstart that alters mouseover events then an event to touchend that removes this alteration. Unfortunately, this doesn't work, because the event order appears to be touchstart → touchend → mouseover → click (I can't attach the normalise-mouseover function to click without messing up other functionality).
I'd expected this question to have been asked before but existing questions don't quite cut it:
How to handle mouseover and mouseleave events in Windows 8.1 Touchscreen is about C# / ASP.Net applications on Windows, not web pages in a browser
JQuery .on(“click”) triggers “mouseover” on touch device is similar but is about jQuery and the answer is a bad approach (guessing a hard-coded list of touchscreen user agents, which would break when new device UAs are created, and which falsely assumes all devices are mouse or touchscreen)
Preventing touch from generating mouseOver and mouseMove events in Android browser is the closest I could find, but it is only about Android, is about preventing not identifying mouseover on touch, and has no answer
Browser handling mouseover event for touch devices causes wrong click event to fire is related, but they're trying to elumate the iOS two-tap interaction pattern, and also the only answer makes that mistake of assuming that touches and mouse/clicks are mutually exclusive.
The best I can think of is to have a touch event that sets some globally accessible variable flag like, say, window.touchedRecently = true; on touchstart but not click, then removes this flag after, say, a 500ms setTimeout. This is an ugly hack though.
Note - we cannot assume that touchscreen devices have no mouse-like roving cursor or visa versa, because there are many devices that use a touchscreen and mouse-like pen that moves a cursor while hovering near the screen, or that use a touchscreen and a mouse (e.g. touchscreen laptops). More details in my answer to How do I detect whether a browser supports mouseover events?.
Note #2 - this is not a jQuery question, my events are coming from Raphael.js paths for which jQuery isn't an option and which give a plain vanilla browser event object. If there is a Raphael-specific solution I'd accept that, but it's very unlikely and a raw-javascript solution would be better.
Given the complexity of the issue, I thought it was worth detailing the issues and edge cases involved in any potential solution.
The issues:
1 - Different implementations of touch events across devices and browsers. What works for some will definitely not work for others. You only need to glance at those patrickhlauke resources to get an idea of how differently the process of tapping a touch-screen is currently handled across devices and browsers.
2 - The event handler gives no clue as to its initial trigger. You are also absolutely right in saying that the event object is identical (certainly in the vast majority of cases) between mouse events dispatched by interaction with a mouse, and mouse events dispatched by a touch interaction.
3 - Any solution to this problem which covers all devices could well be short-lived as the current W3C Recommendations do not go into enough detail on how touch/click events should be handled (https://www.w3.org/TR/touch-events/), so browsers will continue to have different implementations. It also appears that the Touch Events standards document has not changed in the past 5 years, so this isn't going to fix itself soon. https://www.w3.org/standards/history/touch-events
4 - Ideally, solutions should not use timeouts as there is no defined time from touch event to mouse event, and given the spec, there most probably won't be any time soon. Unfortunately, timeouts are almost inevitable as I will explain later.
A future solution:
In the future, the solution will probably be to use Pointer Events instead of mouse / touch events as these give us the pointerType (https://developer.mozilla.org/en-US/docs/Web/API/Pointer_events), but unfortunately we're not there yet in terms of an established standard, and so cross-browser compatibility (https://caniuse.com/#search=pointer%20events) is poor.
How do we solve this at the moment
If we accept that:
You can't detect a touchscreen (http://www.stucox.com/blog/you-cant-detect-a-touchscreen/)
Even if we could, there's still the issue of non-touch events on a touch capable screen
Then we can only use data about the mouse event itself to determine its origin. As we've established, the browser doesn't provide this, so we need to add it ourselves. The only way to do this is using the touch events which are triggered around the same time as the mouse event.
Looking at the patrickhlauke resources again, we can make some statements:
mouseover is always followed by the click events mousedown mouseup and click - always in that order. (Sometimes separated by other events). This is backed up by the W3C recommendations: https://www.w3.org/TR/touch-events/.
For most devices / browsers, the mouseover event is always preceded by either pointerover, its MS counterpart MSPointerOver, or touchstart
The devices / browsers whose event order begins with mouseover have to be ignored. We can't establish that the mouse event was triggered by a touch event before the touch event itself has been triggered.
Given this, we could set a flag during pointerover, MSPointerOver, and touchstart, and remove it during one of the click events. This would work well, except for a handfull of cases:
event.preventDefault is called on one of the touch events - the flag will never be unset as the click events will not be called, and so any future genuine click events on this element would still be marked as a touch event
if the target element is moved during the event. The W3C Recommendations state
If the contents of the document have changed during processing of the
touch events, then the user agent may dispatch the mouse events to a
different target than the touch events.
Unfortunately this means that we will always need to use timeouts. To my knowledge there is no way of either establishing when a touch event has called event.preventDefault, nor understanding when the touch element has been moved within the DOM and the click event triggered on another element.
I think this is a fascinating scenario, so this answer will be amended shortly to contain a recommended code response. For now, I would recommend the answer provided by #ibowankenobi or the answer provided by #Manuel Otto.
What we do know is:
When the user uses no mouse
the mouseover is directly (within 800ms) fired after either a touchend or a
touchstart (if the user tapped and held).
the position of the mouseover and the touchstart/touchend are identical.
When the user uses a mouse/pen
The mouseover is fired before the touch events, even if not, the position of the mouseover will not match the touch events' position 99% of time.
Keeping these points in mind, I made a snippet, which will add a flag triggeredByTouch = true to the event if the listed conditions are met. Additionally you can add this behaviour to other mouse events or set kill = true in order to discard mouseevents triggered by touch completely.
(function (target){
var keep_ms = 1000 // how long to keep the touchevents
var kill = false // wether to kill any mouse events triggered by touch
var touchpoints = []
function registerTouch(e){
var touch = e.touches[0] || e.changedTouches[0]
var point = {x:touch.pageX,y:touch.pageY}
touchpoints.push(point)
setTimeout(function (){
// remove touchpoint from list after keep_ms
touchpoints.splice(touchpoints.indexOf(point),1)
},keep_ms)
}
function handleMouseEvent(e){
for(var i in touchpoints){
//check if mouseevent's position is (almost) identical to any previously registered touch events' positions
if(Math.abs(touchpoints[i].x-e.pageX)<2 && Math.abs(touchpoints[i].y-e.pageY)<2){
//set flag on event
e.triggeredByTouch = true
//if wanted, kill the event
if(kill){
e.cancel = true
e.returnValue = false
e.cancelBubble = true
e.preventDefault()
e.stopPropagation()
}
return
}
}
}
target.addEventListener('touchstart',registerTouch,true)
target.addEventListener('touchend',registerTouch,true)
// which mouse events to monitor
target.addEventListener('mouseover',handleMouseEvent,true)
//target.addEventListener('click',handleMouseEvent,true) - uncomment or add others if wanted
})(document)
Try it out:
function onMouseOver(e){
console.log('triggered by touch:',e.triggeredByTouch ? 'yes' : 'no')
}
(function (target){
var keep_ms = 1000 // how long to keep the touchevents
var kill = false // wether to kill any mouse events triggered by touch
var touchpoints = []
function registerTouch(e){
var touch = e.touches[0] || e.changedTouches[0]
var point = {x:touch.pageX,y:touch.pageY}
touchpoints.push(point)
setTimeout(function (){
// remove touchpoint from list after keep_ms
touchpoints.splice(touchpoints.indexOf(point),1)
},keep_ms)
}
function handleMouseEvent(e){
for(var i in touchpoints){
//check if mouseevent's position is (almost) identical to any previously registered touch events' positions
if(Math.abs(touchpoints[i].x-e.pageX)<2 && Math.abs(touchpoints[i].y-e.pageY)<2){
//set flag on event
e.triggeredByTouch = true
//if wanted, kill the event
if(kill){
e.cancel = true
e.returnValue = false
e.cancelBubble = true
e.preventDefault()
e.stopPropagation()
}
return
}
}
}
target.addEventListener('touchstart',registerTouch,true)
target.addEventListener('touchend',registerTouch,true)
// which mouse events to monitor
target.addEventListener('mouseover',handleMouseEvent,true)
//target.addEventListener('click',handleMouseEvent,true) - uncomment or add others if wanted
})(document)
a{
font-family: Helvatica, Arial;
font-size: 21pt;
}
Click me
According to https://www.html5rocks.com/en/mobile/touchandmouse/
For a single click the order of events is:
touchstart
touchmove
touchend
mouseover
mousemove
mousedown
mouseup
click
So you might be able to set some arbitrary boolean isFromTouchEvent = true; in onTouchStart() and isFromTouchEvent = false; in onClick() and check for that inside of onMouseOver(). This doesn't work very well since we're not guaranteed to get all those events in the element that we're trying to listen on.
I usually have couple of general schemes which I use for this, one of them uses a manual principle of setTimeout to trigger a property. I will explain this one here, but first try to reason about using touchstart, touchmove and touchend on touch devices and use mouseover on destop.
As you know, calling event.preventDefault (event has to be not passive for this to work with touchstart) in any of the touchevents will cancel the subsequent mousecalls so you do not need to deal with them. But in case this is not what you want, here is what I use sometimes (I refer as "library" to your dom manipulation library, and "elem" as your element):
with setTimeout
library.select(elem) //select the element
.property("_detectTouch",function(){//add a _detectTouch method that will set a property on the element for an arbitrary time
return function(){
this._touchDetected = true;
clearTimeout(this._timeout);
this._timeout = setTimeout(function(self){
self._touchDetected = false;//set this accordingly, I deal with either touch or desktop so I can make this 10000. Otherwise make it ~400ms. (iOS mouse emulation delay is around 300ms)
},10000,this);
}
}).on("click",function(){
/*some action*/
}).on("mouseover",function(){
if (this._touchDetected) {
/*coming from touch device*/
} else {
/*desktop*/
}
}).on("touchstart",function(){
this._detectTouch();//the property method as described at the beginning
toggleClass(document.body,"lock-scroll",true);//disable scroll on body by overflow-y hidden;
}).on("touchmove",function(){
disableScroll();//if the above overflow-y hidden don't work, another function to disable scroll on iOS.
}).on("touchend",function(){
library.event.preventDefault();//now we call this, if you do this on touchstart chrome will complain (unless not passive)
this._detectTouch();
var touchObj = library.event.tagetTouches && library.event.tagetTouches.length
? library.event.tagetTouches[0]
: library.event.changedTouches[0];
if (elem.contains(document.elementFromPoint(touchObj.clientX,touchObj.clientY))) {//check if we are still on the element.
this.click();//click will never be fired since default prevented, so we call it here. Alternatively add the same function ref to this event.
}
toggleClass(document.body,"lock-scroll",false);//enable scroll
enableScroll();//enableScroll
})
Another option without setTimeout is to think mousover is counter to touchstart and mouseout counter to touchend. So former events (the touch events) will set a property, if the mouse events detect that property then they do not fire and reset the property to its initial value and so on. In that case something along these lines will also do:
without setTimeout
....
.on("mouseover",function(dd,ii){
if (this._touchStarted) {//touch device
this._touchStarted = false;//set it back to false, so that next round it can fire incase touch is not detected.
return;
}
/*desktop*/
})
.on("mouseout",function(dd,ii){//same as above
if(this._touchEnded){
this._touchEnded = false;
return;
}
})
.on("touchstart",function(dd,ii){
this._touchStarted = true;
/*some action*/
})
.on("touchend",function(dd,ii){
library.event.preventDefault();//at this point emulations should not fire at all, but incase they do, we have the attached properties
this._touchEnded = true;
/*some action*/
});
I removed a lot of details but I guess this is the main idea.
You can use modernizr for that! I just tested this on a local development server and it works.
if (Modernizr.touch) {
console.log('Touch Screen');
} else {
console.log('No Touch Screen');
}
So I would start there?
Pointer Events are widely supported now. So now we can use pointerenter and check event.pointerType:
const element = document.getElementById("hoverableElement")
element.addEventListener("pointerenter", (event) => {
if (event.pointerType === "mouse") {
alert("Hovered")
}
})
<div id="hoverableElement">Trigger on hover, but not on touch</div>
I've written a little drag and drop script in Javascript, I'm aiming to make it as efficient as possible (element following the cursor at the exact spot it was grabbed and no lag spikes) to accomplish this you usually try to limit the amount of times your move function gets fired (throttling the mousemove event) but I tried some other method, thing is I'm not sure if it's actualy doing what I'm expecting.
This is how I'm handling it;
Firstly, on mousedown, a requestAnimationFrame loop starts
var handleMovement = function(){
self.ele.style.top = self.dragElPos.pageTop+'px';
self.ele.style.left = self.dragElPos.pageLeft+'px';
self.animFrame = requestAnimationFrame(handleMovement);
}
And secondly, the mousemove event calls this function
var setCoordinates = function (e) {
self.dragElPos.pageTop = (e.pageY-self.dragElPos.innerTop);
self.dragElPos.pageLeft = (e.pageX-self.dragElPos.innerLeft);
}
All this does is store the position in some object, the handleMovement() function retrieves this and due to the animation loop the element gets moved.
The behaviour I'm expecting is that requestAnimationFrame is optimizing the loop so the animation runs smoothly, but because the coordinates are being set by some other function I wonder if it knows when it's optimized.
It looks pretty smooth, but if it's not being optimized I'd rather use mousemove throttling.
P.S. Browser compatibility is no concern.