JS (No Jquery) - Change CSS when scrolled to a set point - javascript

Sorry, but I am a complete noob with JS. I am using Bootstrap to try build my first website.
The website has a fixed top navbar. I want to change the navbar's border-bottom properties when it reaches the bottom of the header div (about 480/500px down the page).
Currently the border-bottom is white, but I want to change it to blue when scrolled beyond a certain point (bottom of header) and then change back to white if scrolled back up again. The effect I want is the appearance of the fixed nav 'picking up' the bottom border of the banner section when it scroll's past.
I have given the navbar div an id of id="n1", and created a class .navbar1{border-bottom: 1px solid rgba(46,152,255,1)!Important;} to add to override the existing css.
I am not using jQuery because I don't use much JS and I don't want to call it just for a few things - it is a big file. I have tried various things without any success. Probably because they relied on jQuery? I don't know. For example, the last one was:
$(window).scroll( function(){
if($(window).scrollTop() > 50) $("n1").addClass("navbar1");
else $("n1").removeClass("navbar1");
});
Anyway, I was hoping someone may be able to help me with the plain/pure JS to change the attribute properties as described. Thank you in advance for any assistance.
EDIT:
This has been kindly answered below. But given some comments, I thought it might be useful to clarify my use of JS: My website requires very little JS functionality so I have chosen to inline my JS, rather than call an external JS file or files - such as jquery.js and bootstrap.js which are relatively large files.
Although I lose the benefit of caching the JS, and my HTML is slightly larger, I am happy to do that because in my case I feel those losses are more than made up for the increased initial page load speed from:
not having to make additional http requests,
not having to load relatively large files.
It is certainly not for everyone, but I feel that it suits my case. Having said that, when all is done and my website is up and running I will probably do some testing to see whether a custom external JS file is better again. Basically, I am only using Bootstrap for its CSS functionality, not its JS functionality. I hope that makes sense.

This demo may help you!
It doesn't use jQuery.
Here is the javascript code:
window.onscroll = function() {
var nav = document.getElementById('nav');
if ( window.pageYOffset > 100 ) {
nav.classList.add("navbar1");
} else {
nav.classList.remove("navbar1");
}
}

I did a small change on #radonirina-maminiaina amazing answer.
While it works, I do prefer avoiding doing unnecessary DOM calls during the onScroll event. The onScroll event can be triggered quite often on some devices, so it's best to keep its handler as fast as possible.
In my solution, I cache the nav DOM element on a closure and I only update its classes if the offset changes.
window.onscroll = function () {
let isScrolled = false
const scrollPoint = 100
const nav = document.getElementById('navbar')
function onScroll () {
if ( window.pageYOffset > scrollPoint && !isScrolled ) {
nav.classList.add("scroll");
isScrolled = true
} else if (window.pageYOffset <= scrollPoint && isScrolled) {
nav.classList.remove("scroll");
isScrolled = false
}
}
onScroll() // Makes sure that the class is attached on the first render
return onScroll
}()

Related

How to make Bootstrap header that changes size on scroll down?

I've seen a few different threads seemingly about this but none of the answers in them have a working solution for me.
Here's what I want:
Big transparent header with a big logo on the top.
Small colored header with a small logo when user has scrolled past the topmost area.
I'm using navbar-fixed-top and and Bootstrap's scrollspy to add and remove certain classes from the header.
Here's why it hasn't worked so far:
$(window).scrollTop() doesn't return anything meaningful at all.
It seems wrong to change at a certain amount of pixels from the top anyway, since it can vary between screen resolutions.
Initiating a change based on what activate.bs.scrollspy captures works rather well except it shows the wrong header when I load the page for the first time.
It seems impossible to place a <div id="whatever"> at a certain spot and have the header change when scrollspy finds it. I've tried making the div 1px in dimension and placed at the absolute top of the page, but the scrollspy still identifies it from way off.
Here's my jQuery code at the moment, which is very imprecise AND shows the wrong header at the first load of the page (remember, you're not always at the top of the page when loading (reloading) the page!).
$(document).ready(function() {
$('body').scrollspy({ target: '.navbar-inverse' });
$('#main-header').on('activate.bs.scrollspy', function () {
var currentItem = $('.nav li.active > a').text();
var header = $('.navbar');
var logosmall = $('.small-brand');
var logobig = $('.big-brand');
if (currentItem == 'top' && header.hasClass('navbar-small')) {
header.removeClass('navbar-small');
header.addClass('navbar-big');
logosmall.css('display', 'none');
logobig.css('display', 'inline-block');
}
else if (currentItem != 'top' && header.hasClass('navbar-big')) {
header.removeClass('navbar-big');
header.addClass('navbar-small');
logobig.css('display', 'none');
logosmall.css('display', 'inline-block');
}
});
});
Wrap your code into window scroll event as mentioned below then only $(window).scrollTop() will work as you expecting.
$(window).scroll(function () {});
Here is a great example of your problem, it is a bit tricky to shrink your navbar but not impossible. You have to take into account a lot of things. I found this a while ago: http://www.bootply.com/109943
It is really strange that $(window).scrollTop() does not return anything by the way. What browser are you on? And your problem with reloading the browser:
$(window).load(function{
//logic to check how far scrolled
})

jQuery scrolling DIV is jumpy and positioned incorrectly

Not too long ago I asked about setting up a DIV which scrolls with the rest of the page. Post can be found here.
I've set this up, using the following code:
JS..
jQuery(function ($) {
var el = $('#sidebar'),
pos = el.position().top;
alert(pos);
$(window).scroll(function() {
el.toggleClass('fixed', $(this).scrollTop() >= pos);
});
});
CSS..
/* profile sidebar */
#sidebar>div{ width: 300px; margin-top: 10px; }
#sidebar.fixed>div{position:fixed;top:0}
A copy of the page can be found here. The alert was just some debugging.
The problem is, when you scroll a small amount, #sidebar suddenly appears at the very top of the page. In addition, sometimes as you scroll further down, the sidebar appears - and sometimes it doesn't.
Any idea what might be causing such seemingly random functionality?
I'm still trying to figure out why it works in the first place in the jsfiddle example, but anyway, I know how to fix it:
$(window).scroll(function() {
if($(this).scrollTop() >= pos){
el.addClass('fixed');
}else{
el.removeClass('fixed');
}
});
I tested this by unbinding the event you had and replacing it with this code. It seemed to work fine.
The reason I can't understand why it works in the example: toggleClass should be constantly adding and removing "fixed" if you have scrolled enough, because the conditional is true (true here means whether to toggle). The constant adding and removing of the fixed class causes the jumpy behavior.
You can watch this on your page: open up some dev tools (firegubg or Chrome) and watch what happens to your sidebar element.
[UPDATE]
Actually, I misread the docs. True means the class should be added (I don't think the docs are very clear though). Thus... the only way I could explain this is if #dunc was running jQuery v1.2 and the switch was getting ignored completely...

div max-height set dynamically using javascript

I have a web app using master page and content pages (see the attached image). I need to set max-width of one div in content page dynamically accordint to the browser window size (so that the whole app stays on the page, without scrolling). I couldn't find the sloution (or couldn't replicate the results) using just html and CSS. So I'm thinking to do it using javascript. But the problem is, I NEVER used it, so I really have no clue how to do it. I'd really appriciate if someone took a couple of minutes and write the function that will do it. As I see it, I should take difference in height between bottom edge of the header and top edge of the footer and subtract height values of searchbar and button bar.
EDIT:
Thanks to maxedison for providing that code. But, how do I use it? :D I'm a total noob. I have a problem, since I use masterpage and content pages. Where do I put that code?
EDIT 2 - THE ANSWER:
I looked a little further into how to use jQuery, and searched here some more, and I found a solution. Next time I start developing an application, I'll use jQuery from the bottoms up...It just simplifies some things so much. :)
So for the solution: It's similar to what maxedison suggested, but I changed it so, that I set height with CSS and I just added a fixed value to deduct from window.height.
<script type='text/javascript'>
$(function () {
$('.myStyle').css({ 'height': (($(window).height()) - 350) + 'px' });
$(window).resize(function () {
$('.myStyle').css({ 'height': (($(window).height()) - 350) + 'px' });
});
});
</script>
Using jQuery, it would look something like:
function resetHeight(){
var newHeight = $(window).height() - $('.header').outerHeight() - $('.searchBar').outerHeight() - $('.buttons').outerHeight() - $('.footer').outerHeight();
$('.content').height(newHeight);
}
$(function(){
newHeight();
$(window).resize(function(){
resetHeight();
});
});

How to control the jump to a bookmark inside a page

I'm trying to achieve a page with a certain number of divs, each of which has a bookmark (a name). The problem is, when I jump to one of the bookmarks, part of the text is gone, caused by the design. I'd like to know if there's a way to change the behaviour of the bookmark, so it won't set the start of it at the top of the page, but a set number of pixels below.
The page can be accessed here: Not longer online, sorry.
The behaviour occurs when you go to any of the bookmarks (except #6, because the document ends there), like on here: Not longer online, sorry.
Can this be solved by a css property or any other way? (update) I'd prefer this over a javascript solution because I'm planning to use javascript to tab them, and keep the bookmarks in case of disabled javascript
You can do it with JavaScript using scrollBy. Put this in a load listener or onload handler:
if(window.location.hash.length > 1) {
window.scrollBy(0, -60); // Adjust to suit your needs.
}
window.onhashchange = window.onload = function () {
if( window.location.hash.length && window.scrollY > window.pageYOffset ) {
window.scrollBy( 0, -100 ); // Scroll up 100 pixels on hash change
};
};
I got the answer myself, so this is basically for references.
To ignore the 100px offset that is caused by the header, I added a padding-top of 100px to each single div element, and then I changed the links to go to the div's instead of the a elements I added. This padding-top basically makes the text appear where it should and thus solved my problem.

JavaScript to scroll long page to DIV

I have a link on a long HTML page. When I click it, I wish a div on another part of the page to be visible in the window by scrolling into view.
A bit like EnsureVisible in other languages.
I've checked out scrollTop and scrollTo but they seem like red herrings.
Can anyone help?
old question, but if anyone finds this through google (as I did) and who does not want to use anchors or jquery; there's a builtin javascriptfunction to 'jump' to an element;
document.getElementById('youridhere').scrollIntoView();
and what's even better; according to the great compatibility-tables on quirksmode, this is supported by all major browsers!
If you don't want to add an extra extension the following code should work with jQuery.
$('a[href=#target]').
click(function(){
var target = $('a[name=target]');
if (target.length)
{
var top = target.offset().top;
$('html,body').animate({scrollTop: top}, 1000);
return false;
}
});
How about the JQuery ScrollTo - see this sample code
You can use Element.scrollIntoView() method as was mentioned above. If you leave it with no parameters inside you will have an instant ugly scroll. To prevent that you can add this parameter - behavior:"smooth".
Example:
document.getElementById('scroll-here-plz').scrollIntoView({behavior: "smooth", block: "start", inline: "nearest"});
Just replace scroll-here-plz with your div or element on a website. And if you see your element at the bottom of your window or the position is not what you would have expected, play with parameter block: "". You can use block: "start", block: "end" or block: "center".
Remember: Always use parameters inside an object {}.
If you would still have problems, go to https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
There is detailed documentation for this method.
Click here to scroll
<A name='myAnchorALongWayDownThePage"></a>
No fancy scrolling but it should take you there.
The difficulty with scrolling is that you may not only need to scroll the page to show a div, but you may need to scroll inside scrollable divs on any number of levels as well.
The scrollTop property is a available on any DOM element, including the document body. By setting it, you can control how far down something is scrolled. You can also use clientHeight and scrollHeight properties to see how much scrolling is needed (scrolling is possible when clientHeight (viewport) is less than scrollHeight (the height of the content).
You can also use the offsetTop property to figure out where in the container an element is located.
To build a truly general purpose "scroll into view" routine from scratch, you would need to start at the node you want to expose, make sure it's in the visible portion of it's parent, then repeat the same for the parent, etc, all the way until you reach the top.
One step of this would look something like this (untested code, not checking edge cases):
function scrollIntoView(node) {
var parent = node.parent;
var parentCHeight = parent.clientHeight;
var parentSHeight = parent.scrollHeight;
if (parentSHeight > parentCHeight) {
var nodeHeight = node.clientHeight;
var nodeOffset = node.offsetTop;
var scrollOffset = nodeOffset + (nodeHeight / 2) - (parentCHeight / 2);
parent.scrollTop = scrollOffset;
}
if (parent.parent) {
scrollIntoView(parent);
}
}
This worked for me
document.getElementById('divElem').scrollIntoView();
Answer posted here - same solution to your problem.
Edit: the JQuery answer is very nice if you want a smooth scroll - I hadn't seen that in action before.
Why not a named anchor?
The property you need is location.hash. For example:
location.hash = 'top'; //would jump to named anchor "top
I don't know how to do the nice scroll animation without the use of dojo or some toolkit like that, but if you just need it to jump to an anchor, location.hash should do it.
(tested on FF3 and Safari 3.1.2)
I can't add a comment to futtta's reply above, but for a smoother scroll use:
onClick="document.getElementById('more').scrollIntoView({block: 'start', behavior: 'smooth'});"
<button onClick="scrollIntoView()"></button>
<br>
<div id="scroll-to"></div>
function scrollIntoView() {
document.getElementById('scroll-to').scrollIntoView({
behavior: 'smooth'
});
}
The scrollIntoView method accepts scroll-Options to animate the scroll.
With smooth scroll
document.getElementById('scroll-to').scrollIntoView({
behavior: 'smooth'
});
No animation
document.getElementById('scroll-to').scrollIntoView();
There is a jQuery plugin for the general case of scrolling to a DOM element, but if performance is an issue (and when is it not?), I would suggest doing it manually. This involves two steps:
Finding the position of the element you are scrolling to.
Scrolling to that position.
quirksmode gives a good explanation of the mechanism behind the former. Here's my preferred solution:
function absoluteOffset(elem) {
return elem.offsetParent && elem.offsetTop + absoluteOffset(elem.offsetParent);
}
It uses casting from null to 0, which isn't proper etiquette in some circles, but I like it :) The second part uses window.scroll. So the rest of the solution is:
function scrollToElement(elem) {
window.scroll(0, absoluteOffset(elem));
}
Voila!
As stated already, Element.scrollIntoView() is a good answer. Since the question says "I have a link on a long HTML page..." I want to mention a relevant detail. If this is done through a functional link it may not produce the desired effect of scrolling to the target div. For example:
HTML:
<a id="link1" href="#">Scroll With Link</a>
JavaScript:
const link = document.getElementById("link1");
link.onclick = showBox12;
function showBox12()
{
const box = document.getElementById("box12");
box.scrollIntoView();
console.log("Showing Box:" + box);
}
Clicking on Scroll With Link will show the message on the console, but it would seem to have no effect because the # will bring the page back to the top. Interestingly, if using href="" one might actually see the page scroll to the div and jump back to the top.
One solution is to use the standard JavaScript to properly disable the link:
<a id="link1" href="javascript:void(0);">Scroll With Link</a>
Now it will go to box12 and stay there.
I use a lightweight javascript plugin that I found works across devices, browsers and operating systems: zenscroll
scrollTop (IIRC) is where in the document the top of the page is scrolled to. scrollTo scrolls the page so that the top of the page is where you specify.
What you need here is some Javascript manipulated styles. Say if you wanted the div off-screen and scroll in from the right you would set the left attribute of the div to the width of the page and then decrease it by a set amount every few seconds until it is where you want.
This should point you in the right direction.
Additional: I'm sorry, I thought you wanted a separate div to 'pop out' from somewhere (sort of like this site does sometimes), and not move the entire page to a section. Proper use of anchors would achieve that effect.
I personally found Josh's jQuery-based answer above to be the best I saw, and worked perfectly for my application... of course, I was already using jQuery... I certainly wouldn't have included the whole jQ library just for that one purpose.
Cheers!
EDIT: OK... so mere seconds after posting this, I saw another answer just below mine (not sure if still below me after an edit) that said to use:
document.getElementById('your_element_ID_here').scrollIntoView();
This works perfectly and in so much less code than the jQuery version! I had no idea that there was a built-in function in JS called .scrollIntoView(), but there it is! So, if you want the fancy animation, go jQuery. Quick n' dirty... use this one!
For smooth scroll this code is useful
$('a[href*=#scrollToDivId]').click(function() {
if (location.pathname.replace(/^\//,'') == this.pathname.replace(/^\//,'') && location.hostname == this.hostname) {
var target = $(this.hash);
target = target.length ? target : $('[name=' + this.hash.slice(1) +']');
var head_height = $('.header').outerHeight(); // if page has any sticky header get the header height else use 0 here
if (target.length) {
$('html,body').animate({
scrollTop: target.offset().top - head_height
}, 1000);
return false;
}
}
});
Correct me if I'm wrong but I'm reading the question again and again and still think that Angus McCoteup was asking how to set an element to be position: fixed.
Angus McCoteup, check out http://www.cssplay.co.uk/layouts/fixed.html - if you want your DIV to behave like a menu there, have a look at a CSS there

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