Develop Reference

Reducing fixed header on scroll from top of page

I have a website with a fixed header, on the home page the header contains additional content when you are at the top of the page, but I want to hide this content and have a reduced header as they scroll down the page.
So on the initial scroll i want to hide the additional header content and animate the margin of the content below but keep it so that the top of the content still shows underneath it and then scroll from normal from there.
The snippet below should show what I mean better:
var head_height = $('#header').outerHeight(true);
$('#page_content').css('margin-top', (head_height)+'px');
if($('#extra_header_content').length != 0){
$('#header').addClass('home');
var main_head_height = $("#main_header_content").outerHeight(true);
var extra_head_height = $('#header').outerHeight(true);
$(document).on("scroll", function(){
if($(document).scrollTop() >= main_head_height){
$("#extra_header_content").slideUp("slow");
$('#page_content').css('margin-top', (main_head_height)+'px');
$('#header').removeClass('home');
}else{
$("#extra_header_content").slideDown("slow");
$('#page_content').css('margin-top', (extra_head_height)+'px');
$('#header').addClass('home');
}
});
}else{
$('#header').removeClass('home');
}
div{padding:0px;margin:0px;}
#header{background-color:#d33;position:fixed;top:0px;width:100%;}
.home{background-color:#3d3 !important;}
#main_header_content{height:50px;width:100%;}
#extra_header_content{height:50px;width:100%;}
#page_content{background-color:#33d;height:5000px;width:100%;}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="header">
<div id="main_header_content">Main header</div>
<div id="extra_header_content">Extra Header</div>
</div>
<div id="page_content">This should still be visible when header initially reduces</div>

You need to change in your JS code. Margin you are reducing when the page start scrolling need to adjust by padding. So you can try this:
var head_height = $('#header').outerHeight(true);
$('#page_content').css('margin-top', (head_height)+'px');
if($('#extra_header_content').length != 0){
$('#header').addClass('home');
var main_head_height = $("#main_header_content").outerHeight(true);
var extra_head_height = $('#header').outerHeight(true);
$(document).on("scroll", function(){
if($(document).scrollTop() >= main_head_height){
$("#extra_header_content").slideUp("slow");
// $('#page_content').css('margin-top', (main_head_height)+'px');
$('#page_content').css(
{'margin-top': (main_head_height)+'px', 'padding-top': (main_head_height)+'px'}
);
$('#header').removeClass('home');
}else{
$("#extra_header_content").slideDown("slow");
$('#page_content').css('margin-top', (extra_head_height)+'px');
$('#header').addClass('home');
}
});
}else{
$('#header').removeClass('home');
}
div{padding:0px;margin:0px;}
#header{background-color:#d33;position:fixed;top:0px;width:100%;}
.home{background-color:#3d3 !important;}
#main_header_content{height:50px;width:100%;}
#extra_header_content{height:50px;width:100%;}
#page_content{background-color:#33d;height:5000px;width:100%;}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="header">
<div id="main_header_content">Main header</div>
<div id="extra_header_content">Extra Header</div>
</div>
<div id="page_content">This should still be visible when header initially reduces</div>

You can do it like this:
var head_height = $('#header').outerHeight(true);
$('#page_content').css('margin-top', (head_height)+'px');
if($('#extra_header_content').length != 0){
$('#header').addClass('home');
var main_head_height = $("#main_header_content").outerHeight(true);
var extra_head_height = $('#extra_header_content').outerHeight(true);
$(document).on("scroll", function() {
const scrollTop = $(document).scrollTop();
if (scrollTop >= head_height) {
$("#extra_header_content").css('height', 0);
$('#page_content').css('margin-top', main_head_height);
$('#header').removeClass('home');
} else if (scrollTop > 0) {
$("#extra_header_content").css('height', extra_head_height - scrollTop);
$('#page_content').css('margin-top', head_height);
$('#header').removeClass('home');
} else {
$("#extra_header_content").css('height', extra_head_height);
$('#page_content').css('margin-top', head_height);
$('#header').addClass('home');
}
});
}else{
$('#header').removeClass('home');
}
div{padding:0px;margin:0px;}
#header{background-color:#d33;position:fixed;top:0px;width:100%;}
.home{background-color:#3d3 !important;}
#main_header_content{height:100px;width:100%;}
#extra_header_content{height:100px;width:100%; overflow: hidden;}
#page_content{background-color:#33d;height:500px;width:100%;}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="header">
<div id="main_header_content">Main header</div>
<div id="extra_header_content">Extra Header</div>
</div>
<div id="page_content">This should still be visible when header initially reduces</div>

I can offer you a different approach without JavaScript
body,html{
padding:0;
margin:0;
}
#main-header{
position:fixed;
top:0;
left:0;
right:0;
height: 50px;
background: green;
z-index:3;
}
#extra-header{
position:fixed;
top:50px;
left:0;
right:0;
height: 50px;
background: lime;
z-index: 0;
}
#content{
margin-top:100px;
height:2000px;
position:relative;
z-index:1;
background:blue;
}
#content>div{
height:200px;
background: #efefef;
}
#content>div:nth-of-type(2n){
background: red;
}
<div id="main-header">
Main
</div>
<div id="extra-header">
Extra
</div>
<div id="content">
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
</div>

This could be a solution if you will use position sticky and not fixed, but this a bit jerky, So I will post one more solution here with smooth animation
var head_height = $('#header').outerHeight(true);
//$('#page_content').css('padding-top', (head_height)+'px');
if ($('#extra_header_content').length != 0) {
$('#header').addClass('home');
var main_head_height = $("#main_header_content").outerHeight(true);
var extra_head_height = $('#header').outerHeight(true);
$(document).on("scroll", function() {
if ($(document).scrollTop() >= main_head_height) {
$('#page_content').css('padding-top', (main_head_height) + 'px');
$("#extra_header_content").slideUp("slow");
//$('.page_content_wrapper').addClass('scrolled');
//$('.page_content_wrapper').css('top', (main_head_height)+'px');
$('#header').removeClass('home');
} else {
$("#extra_header_content").slideDown("slow");
$('#page_content').css('padding-top', 0);
//$('.page_content_wrapper').css('top', 0);
//$('#header').addClass('home');
}
});
} else {
$('#header').removeClass('home');
}
* {
margin: 0;
padding: 0;
box-sizing: border-box;
}
div {
padding: 0px;
margin: 0px;
}
#header {
background-color: #d33;
position: sticky;
top: 0px;
width: 100%;
z-index: 9;
}
.home {
background-color: #3d3 !important;
}
#main_header_content {
height: 50px;
width: 100%;
}
#extra_header_content {
height: 50px;
width: 100%;
}
#page_content {
background-color: #33d;
height: 5000px;
width: 100%;
}
.page_content_wrapper {
position: relative;
top: 0px;
}
#page_content .page_content_wrapper {
transition: top 1s;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="header">
<div id="main_header_content">Main header</div>
<div id="extra_header_content">Extra Header</div>
</div>
<div id="page_content">
<div class="page_content_wrapper">This should still be visible when header initially reduces</div>
</div>
<span class="hamBurger"></span>

Scroll from div to next div (different height)

I have got page with 5 div's. My div's have different heigh (it's adaptive). How I can go to next div by mouse when I scroll half of the current div?
I trying fullpage.js and onepage.js but it not working for me, because my div must be different height
#first {
width:100vw;
height:700px;
background-color:lightyellow;
text-align:center;
}
#second {
width:100vw;
height:700px;
background-color:lightblue;
text-align:center;
}
#third {
width:100vw;
height:1000px;
background-color:lightpink;
text-align:center;
}
#fourht {
width:100vw;
height:1500px;
background-color:lightgreen;
text-align:center;
}
#fiveth {
width:100vw;
height:800px;
background-color:lightgray;
text-align:center;
}
<div id="first">1 div</div>
<div id="second">2 div</div>
<div id="third">3 div</div>
<div id="fourht">4 div</div>
<div id="fiveth">5 div</div>

you're need get the height current active elem, and give for container transform translate( 0, -height ) on scroll, onepage and fullpage for there are work with this.

var $container = $('.container');
var $elem = $container.find('.elem');
var $active = $container.find('.active').height();
$(window).on('scroll',function(){
$container.css({"transform":"translate(0, -" + $active + "px)"});
});
body{
height: 100%;
}
.container{
transition: 1s all;
}
#first {
width:100vw;
height:700px;
background-color:lightyellow;
text-align:center;
}
#second {
width:100vw;
height:700px;
background-color:lightblue;
text-align:center;
}
#third {
width:100vw;
height:1000px;
background-color:lightpink;
text-align:center;
}
#fourht {
width:100vw;
height:1500px;
background-color:lightgreen;
text-align:center;
}
#fiveth {
width:100vw;
height:800px;
background-color:lightgray;
text-align:center;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="container">
<div id="first" class="elem active">1 div</div>
<div id="second" class="elem">2 div</div>
<div id="third" class="elem">3 div</div>
<div id="fourht" class="elem">4 div</div>
<div id="fiveth" class="elem">5 div</div>
</div>

I created my version. Look at this https://codepen.io/damates/pen/VXdKjR .
Jquery:
$("#nextDiv, #previousDiv").click(function(){
actualTopOffset = $(window).scrollTop();
areas = $(".area");
find = false;
newPosition = 0;
type = $(this).attr("data-type");
areasCount = $(areas).length;
$.each(areas, function(index, val) {
if(type == "next"){//if we click to go next area
if($(areas).length > (index+1)){
if(actualTopOffset < $(areas[index+1]).offset().top && !find){// ask if area has top offset higher. If yes set new position
find = true;
newPosition = $(areas[index+1]).offset().top;
}
}
}else if(type == "prev"){ //if we click to go previous area
areasCount--;
if((areasCount) >= 0){
if(actualTopOffset > $(areas[areasCount]).offset().top && !find){// ask if area has top offset lower. If yes set new position
find = true;
newPosition = $(areas[areasCount]).offset().top;
}
}
}
});
if(find){ //If we found new position scroll on new position
$('html, body').animate({
scrollTop: newPosition
}, 1000);
}
});
CSS:
#first {
width:100vw;
height:700px;
background-color:lightyellow;
text-align:center;
}
#second {
width:100vw;
height:700px;
background-color:lightblue;
text-align:center;
}
#third {
width:100vw;
height:1000px;
background-color:lightpink;
text-align:center;
}
#fourht {
width:100vw;
height:1500px;
background-color:lightgreen;
text-align:center;
}
#fiveth {
width:100vw;
height:800px;
background-color:lightgray;
text-align:center;
}
#nextDiv, #previousDiv{
position: fixed;
top: 20px;
background: red;
}
#previousDiv{
top: 0px;
}
HTML:
<div id="first" class="area">1 div</div>
<div id="second" class="area">2 div</div>
<div id="third" class="area">3 div</div>
<div id="fourht" class="area">4 div</div>
<div id="fiveth" class="area">5 div</div>
<div id="previousDiv" data-type="prev">Previous div</div>
Next div
EDIT VERSION WITH SCROLL
I change the script for scrolling. Look at to https://codepen.io/damates/pen/VXdKjR

jQuery calculate the number of line breaks in a div?

So I have a div wrap whose size is a percentage of the screen width. Inside this wrap is multiple .item divs. As the window gets smaller it breaks into new lines obviously.
I wrote some code which basically takes the width of the wrap and divides it by the sum of the widths of the .item boxes. But the flaw is that it looks at it thinking how many boxes could fit in total, were one to mix and match them perfectly like building blocks, but that's not how it works because the ordering is stagnant.
How could I make this logic work?
CodePen
jQuery:
var itemWidth = 0;
var lineCount = 1;
$(window).on('resize', function(){
var lineWidth = $('.line').width();
var itemWidthSum = 0;
lineCount=1;
$('.item').each(function(index, element) {
if(itemWidthSum < (lineWidth - $(element).outerWidth())) {
itemWidthSum = itemWidthSum + $(element).outerWidth();
} else {
lineCount++;
itemWidthSum = 0;
}
});
});
HTML:
<div id="container">
<div class="rect">
<div class="line">
</div>
<div class="item">Computer Science</div>
<div class="item">Language</div>
<div class="item">Marketing</div>
<div class="item">Biology</div>
<div class="item">Computer Science</div>
<div class="item">Language</div>
<div class="item">Marketing</div>
<div class="item">Biology</div>
<div class="item">Computer Science</div>
<div class="item">Language</div>
<div class="item">Marketing</div>
<div class="item">Biology</div>
<div class="item">Computer Science</div>
<div class="item">Language</div>
<div class="item">Marketing</div>
<div class="item">Biology</div>
</div>
<h1 class="answer"></h1>
CSS:
body {
padding:25px;
}
.answer {
position:fixed;
bottom:0;
left:0;
}
#container {
border: 1px solid rgb(200,200,200);
height: auto;
width: 30%;
margin:0 auto;
}
.item {
padding: 10px;
background-color: #aef2bd;
float: left;
}
.rect {
height: 100px;
width:100%;
position: relative;
}
.rect .line {
position:absolute;
height:50px;
width: 100%;
bottom:0;
border-top: 1px solid red;
}

Figured out my logic mistake by debugging each step.
The correct jQuery:
var itemWidth = 0;
var lineCount = 1;
$(window).on('resize', function(){
var lineWidth = $('.line').width();
var itemWidthSum = 0;
var list = [];
lineCount=1;
$('.item').each(function(index, element) {
if((lineWidth - itemWidthSum) > ($(element).outerWidth())) {
itemWidthSum = itemWidthSum + $(element).outerWidth();
} else {
lineCount++;
itemWidthSum = $(element).outerWidth();
}
});
});

Next / previous arrows to cycle through divs

I want to add two arrows to the sides of the "boxes" divs (below) to cycle through the 3 divs.
Working JSFiddle: https://jsfiddle.net/HBHcC/11/
Can someone help me with this?
HTML:
<div class="container">
<div class="boxes">
<div class="one box">
</div>
<div class="two box">
</div>
<div class="three box">
</div>
</div>
</div>
CSS:
.container{
width:100px;
height:100px;
overflow:hidden;
position:relative;
}
.box {
display:inline-block;
float: left;
width: 100px;
height: 100px;
}
.one{
background-color:green;
}
.two{
background-color:red;
}
.three{
background-color:blue;
}
.boxes{
width:400px;
}
JS:
$(document).ready(function(){
$('.box').on("click", function() {
// Is this the last div, or is there a next one?
if ($(this).next().length) {
var animSpeed = 200; // Make this 0 for an instant change
$('.boxes').animate({marginLeft : "-=100"}, animSpeed);
}
});
});

After adding arrows to the div, here is a new fiddle that should get you started:
$('.rightarrow').on("click", function() {
// Is this the last div, or is there a next one?
var animSpeed = 200; // Make this 0 for an instant change
$('.boxes').animate({marginLeft : "-=100"}, animSpeed);
});
$('.leftarrow').on("click", function() {
// Is this the last div, or is there a next one?
var animSpeed = 200; // Make this 0 for an instant change
$('.boxes').animate({marginLeft : "+=100"}, animSpeed);
});
https://jsfiddle.net/tx2yg06w/1/
Updated w/arrows moved out of divs:
$(document).ready(function(){
var animSpeed = 200;
$('.rightarrow').on("click", function() {
if(parseInt($("#boxes").css("marginLeft")) == -200){ return;}
$('.boxes').animate({marginLeft : "-=100"}, animSpeed);
});
$('.leftarrow').on("click", function() {
if(parseInt($("#boxes").css("marginLeft")) == 0){ return;}
$('.boxes').animate({marginLeft : "+=100"}, animSpeed);
});
});
https://jsfiddle.net/b56r0d72/

Errata has given you a good solution. Just wire up his code to the arrows in the snippet below.
Run snippet to view:
<html>
<body>
<style type="text/css">
.leftarrow, .rightarrow {
font-size: 48px;
color: blue;
text-decoration: none;
}
.rightarrow {
color: red;
float: right;
}
.content {
width: 200px;
padding: 4px;
border: 1px gray solid;
}
.box {
height: 200px;
border: 1px green solid;
}
</style>
<div class="content">
<div>
◀
▶
</div>
<div class="box">slide</div>
</div>
</body>
</html>

How to add Div inside Div Dynamically

I have a Div in which I want to add another small Div's Dynamically. But small Div's strictly needs to be inside the main Div. I have added one small Div inside. But how to add all the 15 div's inside the main Div dynamically I'm not getting. Also the size of small Div's are fixed, if they are more in numbers say 20, then Main Div should have horizontal scroll bar.
Here is the HTML used:
<div id="tables" style="width:740px; height:50px; border:1px solid;margin-left:180px;">
<div id ="1" style="border:1px solid; height:44px; width:50px; margin-left:2px; margin-top:2px; margin-bottom:2px;">1</div>
</div>
And here is my fiddle link: Fiddle.

You need to loop as many times as required, create the elements and then append them to #tables. Something like this:
var $tables = $('#tables');
for (var i = 1; i <= 15; i++) {
$('<div />', { class: 'inner', text: i }).appendTo($tables);
};
Example fiddle
You can add the id property back in if needed, but I would advise against incremental id attributes as they only lead to a maintenance headache. Also, I changed the styling to use actual CSS classes for a better separation of concerns.

You can use the following code in jQuery to append a div :
smallDivWidth = (740 / 15);
for (var i = 1; i <= 15; i++) {
$('#tables').append('<div style="border:1px solid; height:44px;float:left; margin- left:2px; margin-top:2px; margin-bottom:2px;">1</div>');
$('#tables').children().css('width',(smallDivWidth-4)+'px');
};
Just as an example, see this here :
$("#btnDynamicDiv").click(function() {
var smallDivWidth = (740 / 15);
for (var i = 1; i <= 15; i++) {
$('#tables').append('<div style="border:1px solid; height:44px;float:left; margin- left:2px; margin-top:2px; margin-bottom:2px;">1</div>');
$('#tables').children().css('width',(smallDivWidth-4)+'px');
};
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<div id="tables" style="width:740px; height:50px; border:1px solid;margin-left:180px;">
<div id ="1" style="border:1px solid; height:44px; width:50px; margin-left:2px; margin-top:2px; margin-bottom:2px;">1</div>
</div>
<input type="button" id="btnDynamicDiv" value ="Add div dynamically"></input>

Try like this (JSFiddle demo)
HTML:
<div id="tables">
<div class="inner" id="innder-1">1</div>
</div>
<div class="inner inner-template"></div>
<br>
<button id="add-btn">Add inner</button>
CSS:
#tables {
width:200px;
height:50px;
border:1px solid;
white-space: nowrap;
overflow-x: auto;
}
.inner {
border:1px solid;
height:44px;
width:50px;
margin-left:2px;
margin-top:2px;
margin-bottom:2px;
display: inline-block;
vertical-align: top;
white-space: howrap;
}
.inner-template {
display: none;
}
JS:
var $template = $('.inner-template');
$('#add-btn').on('click', function() {
var currentID = $('#tables .inner').length + 1;
var $inner = $template
.clone()
.removeClass('inner-template')
.attr('id', 'inner-' + currentID)
.text(currentID)
.appendTo('#tables');
});