I'm trying to check if element crossed bottom edge of viewport. If it did, I want to add class start
to this element. The problem is that when condition is satisfied class adds to all h2
elements.
Here is my code:
$.fn.checkAnimation = function() {
var context = this;
function isElementInViewport(elem) {
var $elem = context;
// Get the scroll position of the page.
var viewportTop = $(window).scrollTop();
var viewportBottom = viewportTop + $(window).height();
// Get the position of the element on the page.
var elemTop = Math.round( $elem.offset().top );
var elemBottom = elemTop + $elem.height();
return (elemTop < viewportBottom);
}
// Check if it's time to start the animation.
function checkAnimation() {
console.log(isElementInViewport($elem));
var $elem = context;
// If the animation has already been started
if ($elem.hasClass('start')) return;
if (isElementInViewport($elem)) {
// Start the animation
context.addClass('start');
}
}
checkAnimation();
return this;
};
$(window).on('scroll scrollstart touchmove orientationchange resize', function(){
$('h2').checkAnimation();
});
You'll need to change your checkAnimation
jQuery plugin to loop through all elements in the jQuery object and process them individually or call your function like this
$('h2').each(function(){
$(this).checkAnimation();
}
Here is what I mean by processing the elements individually inside the plugin:
$.fn.checkAnimation = function() {
function isElementInViewport($elem) {
var viewportTop = $(window).scrollTop();
var viewportBottom = viewportTop + $(window).height();
var elemTop = Math.round( $elem.offset().top );
var elemBottom = elemTop + $elem.height();
return (elemTop < viewportBottom);
}
function checkAnimation() {
var $elem = $(this);
if ($elem.hasClass('start')) return;
if (isElementInViewport($elem)) {
$elem.addClass('start');
}
}
return this.each(checkAnimation);
};
If you use this version of the plugin you can call it like this:
$('h2').checkAnimation();
It will add the class only to the element that matches the condition not to all the element in the jQuery object you've called the function on.
Should be $elem.addClass('start');
instead and remove the var $elem = context;
statement like :
function checkAnimation() {
console.log(isElementInViewport($elem));
// If the animation has already been started
if ($elem.hasClass('start')) return;
if (isElementInViewport($elem)) {
// Start the animation
$elem.addClass('start');
}
}
Hope this helps.
this
inside a jQuery plugin is the jQuery object that contains the whole collection of elements represented by the previous selector/filter.
In order to treat each element in the collection as an individual instance you need to loop through the initial this
.
Very basic pattern:
$.fn.pluginName = function(options){
// return original collection as jQuery to allow chaining
// loop over collection to access individual elements
return this.each(function(i, elem){
// do something with each element instance
$(elem).doSomething(); // elem === this also
});
}
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