Develop Reference

How to incorporate JS media Queries and Scroll listening?

I'm currently making an element visible when my nav is at the top of the page. I'd like the element to be hidden if the page gets to max-width: 900px;. I've tried using modernizer for JS media queries but I ca't seem to get it to work.
Code:
var a = $(".menu").offset().top;
function scrollListener(){
if($(document).scrollTop() > a)
{$('.hidden-logo').css({"opacity": "1","display": "block"});
$('.menu').css({"margin-left": "-130px"})
} else {
$('.hidden-logo').css({"opacity": "0","display": "none"});
$('.menu').css({"margin-left": "0px"})
}
};
$(document).scroll(scrollListener);

You were checking the scroll position the wrong way - I think you want the logo to disappear when the current scroll is greater than the top of the logo, not less.
I added a msgS div (for demo purposes only) that will show you the current scroll value against the top-of-menu static value. I also added a 100px fudge factor to the menu location to make it more clear in the demo when the current scroll reaches that position. I use these temporary msg divs myself when working out my code, and then remove them when I've got it all sorted and ready for production.
And this is all you need to check the media query in javascript:
var winmed = window.matchMedia("(max-width: 700px)");
if (winmed.matches){ //do something }
And that can go into a listener function exactly like your scroll listener.
var gloShowLogo = true;
var a = $(".menu").offset().top;
var fudge = 100; //100px fudge factor so can SEE div disappear
function scrollListener(){
updateScrollMsg();
var currScroll = $(document).scrollTop();
var topOfMenu = a+fudge;
if( gloShowLogo && currScroll < topOfMenu ){
$('.hidden-logo').css({"opacity": "1","display": "block"});
$('.menu').css({"margin-left": "-130px"})
} else {
$('.hidden-logo').css({"opacity": "0","display": "none"});
$('.menu').css({"margin-left": "0px"})
}
};
function resizeListener(){
updateMediaMsg();
var winmed = window.matchMedia("(max-width: 500px)");
if (winmed.matches){
$('.hidden-logo').css({"opacity": "1","display": "block"});
gloShowLogo = true;
} else {
$('.hidden-logo').css({"opacity": "0","display": "none"});
gloShowLogo = false;
}
}
$(window).scroll(scrollListener);
$(window).resize(resizeListener);
function updateScrollMsg(){
$('#msgS').html( $(document).scrollTop() +' // ' + $(".menu").offset().top );
}
function updateMediaMsg(){
var winmed = window.matchMedia("(max-width: 500px)");
var medmsg = (winmed.matches) ? '< 500' : '> 500';
console.log(medmsg);
$('#msgM').html(medmsg);
}
.menu{background:green;text-align:center;}
.content{height:200vh;background:palegreen;text-align:center;}
.hidden-logo{position:fixed;top:1vh;right:1vw;padding:15px; background:pink;z-index:2;}
#msgS{position:fixed;top:0;left:0;padding:10px;background:wheat;z-index:2;}
#msgM{position:fixed;top:40px;left:0;padding:10px;background:lightblue;z-index:2;}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
<div class="menu">Menu Div</div>
<div class="content">Lengthy content Div..<br><br><br><br>100<br></div>
<div class="hidden-logo">LOGO</div>
<div id="msgS"></div>
<div id="msgM"></div>
Update:
Sorry, I had the media query a bit backwards myself - I think you want the logo to display when the screen-size is < 900px and to be hidden if wider than 900px, yes?
I added a msgM div so you can watch the media query kick-in -- but getting the best width for the demo was a bit of a challenge. I finally settled at 500px as a width that can be demoed (StackOverflow resizes its StackSnippets container as the browser window resizes, which throws things into confusion at each of their resize breakpoints)

draggable interaction broken on Firefox for Android after page scroll

I'm working on a javascript draggable interaction that has to work with both mouse and touch input and does not have any dependencies. So far it works fine on desktops and mobiles.
Except Firefox for Android shows the following behaviour:
page is not scrolled: fine
page is scrolled vertically: element can only be dragged horizontally
page is scrolled horizontally: element can only be dragged vertically
page is scrolled both vertically and horizontally: element can't be
dragged at all
scroll page back to the very top and left: element can be dragged as
expected again
The code:
var evtStart, evtMove, evtEnd;
if ('ontouchend' in window) {
evtStart = 'touchstart';
evtMove = 'touchmove';
evtEnd = 'touchend';
} else {
evtStart = 'mousedown';
evtMove = 'mousemove';
evtEnd = 'mouseup';
}
// BASIC DRAGGABLE INTERACTION
// No further configuration, just drags ....
var panel = document.querySelector('.testpanel');
panel.addEventListener(evtStart, function(e) {
e.preventDefault();
var styles = window.getComputedStyle(panel),
left = parseFloat(styles.left), // css left on mousedown
top = parseFloat(styles.top), // css top on mousedown
psx = e.pageX || e.touches[0].pageX, // pointer x on mousedown
psy = e.pageY || e.touches[0].pageY; // pointer y on mousedown
// function actually draging the elmt
var drag = function (e) {
e.preventDefault();
var pmx = e.pageX || e.touches[0].pageX, // current pointer x while pointer moves
pmy = e.pageY || e.touches[0].pageY; // current pointer y while pointer moves
panel.style.left = left + (pmx - psx) + 'px'; // set new css left of elmt
panel.style.top = top + (pmy - psy) + 'px'; // set new css top of elmt
};
panel.addEventListener(evtMove, drag);
panel.addEventListener(evtEnd, function () {
panel.removeEventListener(evtMove, drag);
});
});
Demo page
Again, it works fine on desktop and mobiles except FF for Android.
Why does it not work on FF for Android? Is it something in my code or is it a bug in FF? So far I could not find anything helpful.
I would greatly appreciate any help.

Finally I found it myself:
Just swap pageX/pageY with clientX/clientY and it works in FF for Android as well.
I guess the implementation in FF for Android is somewhat different, pageX/pageY are not finalized standards yet according to MDN.

Vanilla JS, Add and Remove on Class on Scroll position

Hey i am trying to add a class depending on the scroll position.
It worked in Jquery but i want to move to vanilla, it doesn't work.
What am i missing?
IF the User scrolls to position 30px it should add the class .c-logo--scrolled
Console Error:
Uncaught TypeError: Cannot read property 'add' of undefined
at add_class_on_scroll (app.min.js:17)
at app.min.js:29
var scrollPosition = window.scrollY;
var logoContainer = document.getElementsByClassName('js-logo');
window.addEventListener('scroll', function() {
scrollPosition = window.scrollY;
if (scrollPosition >= 30) {
logoContainer.classList.add('c-logo--scrolled');
} else {
logoContainer.classList.remove('c-logo--scrolled');
}
});

var logoContainer = document.getElementsByClassName('js-logo');
var logoContainer = document.getElementsByClassName('js-logo')[0];
Then:
Place your scripts in the bottom of the body.
Ensure what element is really scrolling - it's not always window.
https://developer.mozilla.org/ru/docs/Web/API/Window/scrollY - no support in IE
http://caniuse.com/#feat=classlist - partial support in IE10+

How to prevent a link outside a function from triggering it on scroll

This seems like an easy fix, but can't seem to figure it out. I have a table that spawns a fixed header whenever you scroll on it. It's working well, however, an unconnected link near the top of this page, via jquery, scrolls the cursor to the bottom of the page til it hits an anchor. As a result, it quickly moves over the table, spawning the fixed menu, then after reaching the anchor, the fixed menu awkwardly sits there for a second or two, then disappears.
I'm trying to prevent that by disabling the function on click of the link. I've tried e.preventDefault (), but no joy. Here's the fiddle and code (so looking to prevent the fixed "Header / Description" row when you click the link).
Fiddle
// top edge of table
var element_menu_hdr = $(".row-1").offset().top;
var element_menu_end_check = $(".row-12").offset().top;
$(window).on("scroll", function fixmenu() {
var y_scroll_pos = window.pageYOffset;
var scroll_menu_hdr = element_menu_hdr;
var scroll_menu_end_check = element_menu_end_check;
if(y_scroll_pos >= scroll_menu_hdr) {
if($('.affix').length === 0){
$('.row-1.odd').wrap('<table class="tablemain affix view"></table>');
}
} else if (y_scroll_pos < scroll_menu_hdr) {
$('.tablemain.affix.view').contents().unwrap();
} else {
}
});
// bottom edge of table
var element_menu_end = $(".row-12").offset().top;
$(window).on("scroll", function fixmenubtm() {
var y_scroll_pos2 = window.pageYOffset;
var scroll_menu_end = element_menu_end;
if(y_scroll_pos2 > scroll_menu_end) {
$('.tablemain.affix.view tbody').contents().unwrap();
} else {
}
var myVar = y_scroll_pos2;
console.log(myVar, "y_scroll_pos2");
var myVar2 = element_menu_end;
console.log(myVar2, "element_menu_end");
});
jQuery(document).ready(function($) {
$(".scroll").click(function(event){
event.preventDefault();
$('html,body').animate({scrollTop:$(this.hash).offset().top}, 500);
});
});

Getting current page position in IE8 when scrolling

Reference is this page:
http://demo.mypreviewbetasite.com/laverona/menu.html
File in question: http://demo.mypreviewbetasite.com/laverona/scripts/menu.js
The page works as expected in Firefox and Chrome, where as the user scrolls, the position of the window is checked against the position of my sub-menu, so that before it gets scrolled out of view, its position is set to fixed.
However, in IE8, the window position never gets updated as the user scrolls. My testing has shown that IE gets through all the functions, but only updates the windowPos variable when the page loads.
What can be done so that this page behaves the same in IE as it does in FF and Chrome?

this is from jquery documentation:
"The .offset() method allows us to retrieve the current position of an element RELATIVE TO THE DOCUMENT."
I can't understand why FF or Chrome return $('html').offset().top relative to the client screen/ It seems that IE's approach is more predictable.
Try that (use .scrollTop property of the DOM element instead of .offset().top):
$(document).ready(function(e){
//alert("subPos: " + subPos);
//first find the position of the things to sticky
submenu = $("#sub");
//submenu.removeClass("no-js");
subPos = $("#sub").position();
subPos = subPos.top;
var preScrollHtml = document.getElementsByTagName('html').item(0).scrollTop;
var preScrollBody = document.getElementsByTagName('body').item(0).scrollTop;
var checkPos = function(){
var scrolledHtml = document.getElementsByTagName('html').item(0).scrollTop;
var scrolledBody = document.getElementsByTagName('body').item(0).scrollTop;
if (preScrollHtml !== scrolledHtml) {
windowPos = scrolledHtml;
}
else {
windowPos = scrolledBody;
}
preScrollHtml = scrolledHtml;
preScrollBody = scrolledBody;
calculate();
}
var calculate = function() {
subPos = 64;
if (windowPos >= subPos){
$("#sub").addClass("fixed");
$("#minestre").css("marginTop", "50px");
}
else if (windowPos < subPos){
$("#sub").removeClass("fixed");
$("#minestre").css("marginTop", "0px");
}
//Setting text fields to show the values of everything can help in debugging
$("#windowpos").val(windowPos);
$("#subp").val(subPos);
}
//every time the window scrolls, this function is run
if ($(window).scroll){
$(window).scroll(checkPos);
}
else if(window.onscroll){
window.onscroll = checkPos;
}
});

I know this is old, but for new people coming to this question, you may want to check out Andy's answer to a similar question (which also seems to solve this one): https://stackoverflow.com/a/11396681/1793128