Created
February 16, 2017 19:32
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Fade in div on scroll
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| <html> | |
| <head> | |
| <style> | |
| #container | |
| { | |
| height:2000px; | |
| } | |
| #container div | |
| { | |
| margin:50px; | |
| padding:50px; | |
| background-color:lightgreen; | |
| opacity: 1; | |
| transition: opacity 300ms linear; | |
| } | |
| #container div.hidden | |
| { | |
| opacity:0; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <div id="container"> | |
| <div>Hello</div> | |
| <div>Hello</div> | |
| <div>Hello</div> | |
| <div>Hello</div> | |
| <div>Hello</div> | |
| <div>Hello</div> | |
| <div class="hidden">Fade In</div> | |
| <div class="hidden">Fade In</div> | |
| <div class="hidden">Fade In</div> | |
| <div class="hidden">Fade In</div> | |
| <div class="hidden">Fade In</div> | |
| </div> | |
| <script src="https://code.jquery.com/jquery-2.2.4.min.js"></script> | |
| <script> | |
| // Elmentem az ablak méretet | |
| const windowHeight = window.innerHeight; | |
| // Inicializálom a magasságértékeket, hogy ne kelljen minden scroll event-nél kiszámolni. | |
| let hiddenElements = document.querySelectorAll('#container div.hidden'); | |
| if( hiddenElements != null ) hiddenElements.forEach(function(element) { | |
| element.offsetBottom = element.offsetTop+element.offsetHeight; | |
| console.debug(element, '=>', element.offsetBottom); | |
| }); | |
| document.addEventListener('scroll', function(event) { | |
| // Lekérem a görgetés pozicíóját | |
| let scrollTop = Math.max(document.documentElement.scrollTop,document.body.scrollTop); | |
| let scrollBottom = scrollTop+windowHeight; | |
| // Végigmegyek a még meglévő rejtett elemeken | |
| let hiddenElements = document.querySelectorAll('#container div.hidden'); | |
| if( hiddenElements != null ) hiddenElements.forEach(function(element) { | |
| // Ha az elem megjeleníthető, akkor leveszem a class-t és a CSS animál külön szálon a görgetéstől | |
| if( element.offsetBottom <= scrollBottom ) element.classList.remove('hidden'); | |
| }); | |
| }, | |
| // Hozzáadok egy plusz opciót amivel megmondom a böngészőnek, hogy nem fogom meghívni az event.preventDefault() metódust így nem kell megvárnia míg lefut a funkció | |
| {'passive':true}); | |
| </script> | |
| </body> | |
| </html> |
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