Develop Reference

Touch move fire only once when implementing "less" like scrolling on mobile

I'm trying to to implement touch scroll in less extension to jQuery Terminal. It work similar to less unix command.
I have this code:
self.touch_scroll(function(event) {
// how much difference changed since last touch move
var delta = event.current.clientY - event.previous.clientY;
var ret;
var interpreter = interpreters.top();
if (is_function(interpreter.touchscroll)) {
ret = interpreter.touchscroll(event, delta, self);
} else if (is_function(settings.touchscroll)) {
ret = settings.touchscroll(event, delta, self);
}
if (ret === true) {
return;
}
return false;
});
// make_callback_plugin is helper that use $.Callbacks and make sure that there is only
// one handler on the element
$.fn.touch_scroll = make_callback_plugin({
name: 'touch',
init: function(handler) {
var origin;
var previous;
$(this).on('touchstart.scroll', function(e) {
e = e.originalEvent;
if (e.touches.length === 1) {
previous = origin = e.touches[0];
}
}).on('touchmove.scroll', function(e) {
e = e.originalEvent;
console.log(!!origin + ' && ' + (e.touches.length) + ' === 1');
if (origin && e.touches.length === 1) {
var current = e.touches[0];
var ret = handler({
origin: origin,
previous: previous,
current: current
});
if (ret === false) {
// this don't change anything
e.preventDefault();
}
previous = current;
}
}).on('touchend.scroll', function() {
if (origin || previous) {
origin = previous = null;
}
});
},
destroy: function() {
$(this).off('touchstart.scroll touchmove.scroll touchend.scroll');
}
});
and inside less I have:
function scroll(delta, scroll_by) {
if (delta > 0) {
pos -= scroll_by;
if (pos < 0) {
pos = 0;
}
} else {
pos += scroll_by;
if (pos - 1 > lines.length - rows) {
pos = lines.length - rows + 1;
}
}
print();
return true;
}
term.push($.noop, {
onResize: refresh_view,
touchscroll: function(event, delta) {
console.log({delta});
var offset = Math.abs(delta);
// 14 is default height of single line in pixels
scroll(delta, Math.ceil(offset / 14));
return false;
},
mousewheel: function(event, delta) {
return scroll(delta, scroll_by);
},
I also have this css:
.terminal-less {
touch-action: none;
overscroll-behavior-y: contain;
}
on Mousewheel scrolling works good it scroll with the same amount of scroll_by which is by default 3 (seems about right). (pos is lines offset so if I use pos++ it move/scroll by one line, delta in touchscroll is positive or negative from about -20 to 20 pixels.
The problem I have and the question is, how can I make it scroll with the finger? it don't feel right. Also it scroll only once it don't move with the finger. touchmove fire only once, shoudn't it fire while I move the finger while touching the phone?
Anyone have experience with this type of touch scroll behavior?
I was searching for similar problem and didn't found solution. Do you know why touchmove could fire once? The only thing I can think of was textarea that is used as clipboard (on mobile it's also used to enable virtual keyboard), but I've set background to red and it don't move on Android. I was testing other code from this drawing demo:
https://zipso.net/a-simple-touchscreen-sketchpad-using-javascript-and-html5/
and it works fine, touch move keeps firing while you move the finger.
Any ideas? It will be hard to replicate but if somone is interested in investigation I can put all my code on github in jQuery Terminal repo (in some branch).
What's weird is that touchend don't fire after touchmove, it fire once only when I click on the terminal to enable keyboard.
I've tried to monkey patch jQuery on and log each time it fire but I didn't have any other event (that may prevent default behavior) also according to docs mouse events fire after touchend and those don't fire.

What you need is simple .terminal-wrapper { pointer-events: none; } (based on the devel branch). But with this rule you can't select the text, that's why you need to use it only for mobile devices.
I'm not sure if this will block the selection of text on mobile, but if so, you can try to add this on touchstart (or even on touchmove as the first instruction) and remove it on touchend.
Also, I had to add some JS code, because without it interpreter.touchScroll is undefined. But this is not the main cause of the problem.
interpreters = new Stack($.extend({}, settings.extra, {
name: settings.name,
prompt: prompt,
keypress: settings.keypress,
keydown: settings.keydown,
resize: settings.onResize,
greetings: settings.greetings,
mousewheel: settings.mousewheel,
touchScroll: settings.touchScroll, // NEW LINE
history: settings.history,
keymap: new_keymap
}, interpreter));
self.touch_scroll(function(event) {
var delta = event.current.clientY - event.previous.clientY;
var ret;
var interpreter = interpreters.top(); // NEW LINE
if (is_function(interpreter.touchScroll)) {
ret = interpreter.touchScroll(event, delta, self);
} else if (is_function(settings.touchScroll)) {
ret = settings.touchScroll(event, delta, self);
}
if (ret === true) {
return;
}
});
Without pointer-events: none;
With pointer-events: none;

mousewheel event not working on firefox

Below code is working fine on chrome however it doesn't work on Mozilla for some reason that I am not aware yet. Am i missing something ?
$(window).bind('mousewheel', function(event) {
if (event.originalEvent.wheelDelta >= 0) {
$('#currentMove').html('Movement: Scroll up');
$('#currentMove').css('background','#98FB98');
scrollUp++;
$('#scrollUp').html(scrollUp);
}
else {
$('#currentMove').html('Movement: Scroll down');
$('#currentMove').css('background','#FFB6C1');
scrollDown++;
$('#scrollDown').html(scrollDown);
}
});
Here is my fiddle: https://jsfiddle.net/w0wffbxc/ Appreciate your help with this.

Here's your sqlfiddle fixed.
You should use wheel as mousewheel is not recognized by Firefox since version 3. Also with wheel, you should use event.originalEvent.deltaY instead.

Use wheel event instead. Its more of a standard now. This page also provides polyfills for old browsers https://developer.mozilla.org/en-US/docs/Web/Events/wheel
Ex
$(window).on('wheel', function(event){
// deltaY obviously records vertical scroll, deltaX and deltaZ exist too
if(event.originalEvent.deltaY < 0){
// wheeled up
console.log("Works Up");
}
else {
// wheeled down
console.log("Works Down");
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Catch mousewheel up or down with jQuery/JS, without actually scrolling

I'm trying to catch whether the mousewheel is triggered and whether it's scrolled up or down without actually scrolling the page (body has an overflow: hidden).
Any idea's how I can achieve this using jQuery or pure javascript?
$(window).scroll(function(){
if( /* scroll up */){ }
else { /* scroll down */ }
});

I rarely promote plugins but this one is just excellent (and relatively small in size) :
https://plugins.jquery.com/mousewheel/
It'll allow to do something like this :
$(window).mousewheel(function(turn, delta) {
if (delta == 1) // going up
else // going down
// all kinds of code
return false;
});
http://codepen.io/anon/pen/YPmjym?editors=001
Update - at this point the mousewheel plugin could be replaced with the wheel event if legacy browsers need not be supported:
$(window).on('wheel', function(e) {
var delta = e.originalEvent.deltaY;
if (delta > 0) // going down
else // going up
return false;
});

This disables the scrolling.
NOTE: Notice it only stops scrolling if you hover over the element.
$('#container').hover(function() {
$(document).bind('mousewheel DOMMouseScroll',function(){
console.log('Scroll!');
stopWheel();
});
}, function() {
$(document).unbind('mousewheel DOMMouseScroll');
});
function stopWheel(e){
if(!e){ /* IE7, IE8, Chrome, Safari */
e = window.event;
}
if(e.preventDefault) { /* Chrome, Safari, Firefox */
e.preventDefault();
}
e.returnValue = false; /* IE7, IE8 */
}
Quoted from amosrivera's answer
EDIT: To check which way it is scrolling.
var lastScrollTop = 0;
$(window).scroll(function(event){
var st = $(this).scrollTop();
if (st > lastScrollTop){
// downscroll code
} else {
// upscroll code
}
lastScrollTop = st;
});

How to determine scroll direction without actually scrolling

I am coding a page where the first time the user scrolls, it doesn't actually scroll the page down, instead it adds a class with a transition.
I'd like to detect when the user is scrolling down, because if he scrolls up, I want it to do something else.
All the methods that I've found are based on defining the current body ScrollTop, and then comparing with the body scrollTop after the page scrolls, defining the direction, but since the page doesn't actually scroll, the body scrollTop() doesn't change.
animationIsDone = false;
function preventScroll(e) {
e.preventDefault();
e.stopPropagation();
}
$('body').on('mousewheel', function(e) {
if (animationIsDone === false) {
$("#main-header").removeClass("yellow-overlay").addClass("yellow-overlay-darker");
$(".site-info").first().addClass("is-description-visible");
preventScroll(e);
setTimeout(function() {
animationIsDone = true;
}, 1000);
}
});
This is what I have come with, but that way it doesn't matter the direction I scroll it triggers the event

The mousewheel event is quickly becoming obsolete. You should use wheel event instead.
This would also easily allow you to the vertical and/or horizontal scroll direction without scroll bars.
This event has support in all current major browsers and should remain the standard far into the future.
Here is a demo:
window.addEventListener('wheel', function(event)
{
if (event.deltaY < 0)
{
console.log('scrolling up');
document.getElementById('status').textContent= 'scrolling up';
}
else if (event.deltaY > 0)
{
console.log('scrolling down');
document.getElementById('status').textContent= 'scrolling down';
}
});
<div id="status"></div>

Try This using addEventListener.
window.addEventListener('mousewheel', function(e){
wDelta = e.wheelDelta < 0 ? 'down' : 'up';
console.log(wDelta);
});
Demo
Update:
As mentioned in one of the answers, the mousewheel event is depreciated. You should use the wheel event instead.

I know this post is from 5 years ago but I didn't see any good Jquery answer (the .on('mousewheel') doesn't work for me...)
Simple answer with jquery, and use window instead of body to be sure you are taking scroll event :
$(window).on('wheel', function(e) {
var scroll = e.originalEvent.deltaY < 0 ? 'up' : 'down';
console.log(scroll);
});

Try using e.wheelDelta
var animationIsDone = false, scrollDirection = 0;
function preventScroll(e) {
e.preventDefault();
e.stopPropagation();
}
$('body').on('mousewheel', function(e) {
if (e.wheelDelta >= 0) {
console.log('Scroll up'); //your scroll data here
}
else {
console.log('Scroll down'); //your scroll data here
}
if (animationIsDone === false) {
$("#main-header").removeClass("yellow-overlay").addClass("yellow-overlay-darker");
$(".site-info").first().addClass("is-description-visible");
preventScroll(e);
setTimeout(function() {
animationIsDone = true;
}, 1000);
}
});
Note: remember that MouseWheel is deprecated and not supported in FireFox

this one work in react app
<p onWheel={this.onMouseWheel}></p>
after add event listener, in function u can use deltaY To capture mouse Wheel
onMouseWheel = (e) => {
e.deltaY > 0
? console.log("Down")
: console.log("up")
}

Tested on chrome and
$('body').on('mousewheel', function(e) {
if (e.originalEvent.deltaY >= 0) {
console.log('Scroll up'); //your scroll data here
}
else {
console.log('Scroll down'); //your scroll data here
}
});

Distinguishing between the user scrolling and programmatically scrolling using Javascript

I'm creating a scrolling effect using JQuery and I'm wondering if it's possible to distinguish between the user scrolling vs. programmatically scrolling.
I have something like this:
$('#element').on('scroll',function(e){
$('#element').stop(true); // stop previous scrolling animation
$('#element').animate({ // start new scrolling animation (maybe different speed, different direction, etc)
scrollTop:...
});
});
However, this event is triggered during every step of the animation. How can I tell if this event was triggered by the user or by the animation?

Use a variable to determine when you are scrolling programmatically
Example:
var programScrolling = false;
$('#element').on('scroll',function(e){
if (programScrolling) {
return;
}
$('#element').stop(true); // stop scrolling animation
programScrolling = true;
$('#element').animate({
scrollTop:...
});
programScrolling = false;
});
Not sure if that is exactly what you want, but the concept should work.

I would make functions for different kinds of scrollings to detect them and call a scroll handler for all of them, like so:
JS Fiddle
$(window).bind('mousewheel DOMMouseScroll', function(event){
var direction;
if (event.originalEvent.wheelDelta > 0 || event.originalEvent.detail < 0) {
direction = 'up';
}
else {
direction = 'down';
}
scrollHandler(direction, 'mouseWheel');
event.preventDefault();
});
var scrollHandler = function(direction, origin) {
var height = $(document).scrollTop();
var movement = (direction == 'up') ? -100 : 100;
console.log(origin);
$('body').stop(true);
$('body').animate({
scrollTop: height + movement
}, 250);
};
Then you can do different stuff according to the origin of the event!
You could also check if the user scrolls to the same direction that the screen is scrolling and do something different, or whatever you want with the info passed by the mousewheel event.
Original mousewheel event function copied from THIS answer

I would suggest possibly using the .originalEvent method. The downside is, this is very browser dependent. See here. Hopefully the following helps:
$('#element').scroll(function(e){
var humanScroll = e.originalEvent === undefined;
if(humanScroll) {
$(this).stop(true);
}
})