The animationstart event is fired when a CSS Animation has started. If there is an animation-delay, this event will fire once the delay period has expired. A negative delay will cause the event to fire with an elapsedTime equal to the absolute value of the delay (and, correspondingly, the animation will begin playing at that time index into the sequence).
The animationcancel event is fired when a CSS Animation unexpectedly aborts. In other words, any time it stops running without sending an animationend event. This might happen when the animation-name is changed such that the animation is removed, or when the animating node is hidden using CSS. Therefore, either directly or because any of its containing nodes are hidden.
The animationend event is fired when a CSS Animation has completed. If the animation aborts before reaching completion, such as if the element is removed from the DOM or the animation is removed from the element, the animationend event is not fired.
The animationiteration event is fired when an iteration of a CSS Animation ends, and another one begins. This event does not occur at the same time as the animationend event, and therefore does not occur for animations with an animation-iteration-count of one.
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