Develop Reference

Make jQuery act dynamically depending on the width of the window

Hello! I've been learning jQuery for a little while now and am trying to sharpen my skills by creating a responsive website. I added a navigation bar, then a big slider, and below it is the main content of the website. Right now, jQuery (as both the menu background and the main background are black) adds a class to the navigation bar in order to turn it white as soon as you scroll past the slider (which has a height of 550px), so it will be easier to read.
Here's the thing: I want jQuery to add that class depending on the width of the window. If it's less than 600px wide, I want the class to be added automatically. Otherwise, I want jQuery to add it as soon as you scroll past the slider (since I hide it when the window is less than 600px wide). My code is below, and it works just fine if I resize the window and then refresh the page, but I want it to add the class dynamically. Do you think it is possible?
I hope I made myself clear (English is not my first language). Let me know if you need me to explain things better! Thank you in advance. :)
if ($(window).width() > 599 ) {
$(window).scroll(function() {
if ($(window).scrollTop() >= 550) { //if you scroll past the slider
$("#main nav").addClass("white-menu");
} else {
$("#main nav").removeClass("white-menu"); //so it turns black again
}
});
} else {
// add it automatically (the slider is hidden):
$("#main nav").addClass("white-menu");
};

you can use all the code inside scroll event
$(window).scroll(function() {
if ($(this).scrollTop() >= 550 && $(this).width() <= 599) { //if you scroll past the slider
$("#main nav").addClass("white-menu");
} else {
$("#main nav").removeClass("white-menu"); //so it turns black again
}
});
a similar DEMO
about resize you can use
$(window).on('resize',function() {
$("#main nav").removeClass("white-menu");
});
on window resize the code will remove the class till user scroll then the scroll event will fire after user scrolling
or instead of all of that you can just use
$(window).on('scroll resize',function() {
if ($(this).scrollTop() >= 550 && $(this).width() <= 599) { //if you scroll past the slider
$("#main nav").addClass("white-menu");
} else {
$("#main nav").removeClass("white-menu"); //so it turns black again
}
});
DEMO

.scroll allows you to listen to event, if you only listen when the window is the correct size, this listener won't get triggered if that changes, so I changed it around a bit:
$(window).scroll(function() {
if ($(window).width() > 599 ) {
if ($(window).scrollTop() >= 550) { //if you scroll past the slider
$("#main nav").addClass("white-menu");
} else {
$("#main nav").removeClass("white-menu"); //so it turns black again
}
}
});
Like Brian mentioned you should use CSS for this other case:
#media (max-width: 600px) {
#main nav {
// white-menu styles here
}
}
For reference the JS way would be:
$(window).resize(function() {
if ($(window).width() <= 599 ) {
$("#main nav").addClass("white-menu");
}
});
It also might be worth thinking about doing a throttle/debounce on these event listeners. They will get called a lot and if your JS starts to do anything more complicated you will see a performance hit. This example uses the underscore library:
var onScroll = function() {
if ($(window).width() > 599 ) {
if ($(window).scrollTop() >= 550) { //if you scroll past the slider
$("#main nav").addClass("white-menu");
} else {
$("#main nav").removeClass("white-menu"); //so it turns black again
}
}
}
// Don't run until the window has stopped being resized for at least 50ms
var debouncedOnScroll = _.debounce(onScroll, 50);
$(window).scroll(debouncedOnScroll);
See http://underscorejs.org/#debounce

Interesting. I used your code in a fiddle and it worked find. As it's state in another answer, the improve of your code will be using the scroll function to wrap all the actions:
$(window).scroll(function() {
$("#main nav").toggleClass("white-menu", ($(window).scrollTop() >= 550 && $(window).width() <= 599));
});

issue scrollto using fixed nav

I have built a one page site using scrollto and scrollspy. The page works great once the navbar gets fixed to the top. But if you click on any links before the navbar gets fixed to top all the links are off. And there is no consistency in the height that they are off. I have played around with the offset, I do have a padding of 100px to each section to account for spacing issues.
Here is a link to the dev site...
http://23.23.170.24/aspire/
Here is the js...
$(document).ready(function(){
$(window).scroll(function(){
var window_top = $(window).scrollTop() +1; // the "12" should equal the margin-top value for nav.stick
var div_top = $('#checkdiv').offset().top;
if (window_top > div_top) {
$('nav.navbar').addClass('navbar-fixed-top');
$('section').addClass('scrolled');
} else {
$('nav.navbar').removeClass('navbar-fixed-top');
$('section').removeClass('scrolled');
}
});
$(".click").click(function(evn){
evn.preventDefault();
$('html,body').stop(true).scrollTo((this.hash, this.hash),1000, {axis: 'y', offset :0});
return false;
});
$('body').scrollspy({ target: '#navbar' })
});

When the header is stuck, Bootstrap scrollspy and scrollto are automatically taking into account the height of the header. When unstuck, all you have to do is subtract the height of the header and you'll scroll to the correct spot on your page.

Modifying this scrolling nav menu script?

I am a noob and for a school project I was trying to create a single page site that had a static nav menu at the top that always stayed there and I wanted it to do an animated scroll effect when you click it's link. Someone here made this for me and it works perfect.
However, you notice it says .top - 98 and that is because my nav is 98px tall so that it doesn't cut off the section it's jumping to.
Now that I am getting into media queries, I may increase the height of that nav at certain breaks. So I am wondering, is it possible to change this from 98 to some sort of [nav current height] variable? So that it will work regardless of what the height of my nav is?
Thanks in advance!!
$(document).ready(function() {
$("nav a").on('click', function() {
var link = $(this).attr('href');
$('html,body').animate({
scrollTop: ($(link).offset().top - 98)
}, 'slow');
return false;
});
});

how about
$('html,body').animate({scrollTop: ($(link).offset().top - $('nav').height())},'slow');

Yes you can do that
scrollBarFunc = function(){
var myNavHeight = $("#myselectorId").height(); //just put here your id or class
$("nav a").on('click',function(){
var link = $(this).attr('href');
$('html,body').animate({scrollTop: ($(link).offset().top - myNavHeight)},'slow');
return false;
});
}
$(document).ready(function(){
scrollBarFunc();
});
$(window).resize(function(){
scrollBarFunc(); //recall function to work when you resize
});

How to check if i am passing in anchor

I have a menu like bootstrap 3.0 (http://getbootstrap.com/getting-started/) which follows
the scroll down and up, but i'd like to have my menu with class "active" corresponding to the div and anchor in the current position of the page.
How can i do this?
this is responsible to follow the scroll
$(window).scroll(function () {
if ($(this).scrollTop() > 90) {
marginTop = ($(document).scrollTop() - scroll) + marginTop;
scroll = $(document).scrollTop();
$("#sideMenu").animate({
"margin-top": marginTop + "px"
}, {
duration: 0,
queue: false
});
}

I believe you're asking about the "scroll spy" feature. You need to determine if the user has scrolled to the content.
A quick example using jQuery would be to compare the $(document).scrollTop with the offset().top of the element you care about.
Here's one possible library for doing this

Sidebar jumps uncontrollably when the height is modified on scroll

I have a sidebar on my site that is fixed to the side and when the user scrolls down or up, the style attribute top is changed so that the height is adjusted.
$(window).scroll(function() {
if ($(this).scrollTop() < 125){
var v = 125 - $(this).scrollTop();
$("#sidebar").css({'top':v + 'px'});
}
if ($(this).scrollTop() >= 125)
{
$("#sidebar").css({'top':'5px'});
}
});
However, when I scroll down, the sidebar seems to jump uncontrollably and does not stick to the screen as I would like. I am using Chrome 32 so I don't see what the problem is. Please can someone help me with this issue.

Check out this fiddle.
Create a CSS class called fixed.
.fixed {
position: fixed;
top: 0px;
}
On scroll, in your JavaScript add and remove the "fixed" class accordingly to make the proper effect.
JavaScript:
$(function () {
var $sidebar = $('#sidebar');
$(window).on('scroll', function () {
if($(this).scrollTop() < 125) {
$sidebar.removeClass('fixed');
} else {
$sidebar.addClass('fixed');
}
});
});
As the header scrolls out of the window, the sidebar gets the "fixed" class and sticks to the side of the screen at the top left (0,0) respectively. When the header is coming back into view, the class is removed and the sidebar moves gracefully back to it's original position.