How to use JavaScript for animations and transitions?
13/03/2024
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5
min
Animations and transitions in JavaScript could be done in various ways. One of the simplest ways is by using the CSS property transition. This allows an HTML element to gradually change from one style to another.
Below is an html example of how this can be achieved:
<!DOCTYPE html>
<html>
<body>
<h1>JavaScript Animation Example</h1>
<div id="animatedDiv" style="background:#98bf21;height:100px;width:100px;position:absolute;">
</div>
<button onclick="moveAnimation()">Click me to Move</button>
<script>
function moveAnimation() {
var elem = document.getElementById("animatedDiv");
var pos = 0;
var id = setInterval(frame, 5);
function frame() {
if (pos == 350) {
clearInterval(id);
} else {
pos++;
elem.style.top = pos + 'px';
elem.style.left = pos + 'px';
}
}
}
</script>
</body>
</html>
Explanation:
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This creates a square div and moves it diagonally down the webpage 1 unit at a time until pos==350.
setInterval(frame, 5): this functionframeis set to run every 5 milliseconds.frame: this function changes the top and left positions of the div. Ifpos==350it also clears the interval set bysetInterval(frame, 5)so the function stops running.moveAnimation(): This function is called when the button is clicked. It sets the interval and moves the div.
For more complex animations you would typically use an animation/transition library (or write your own) to handle most of the issues that come with animations, such as keyframe animations, stopping, starting, reversing, looping, pausing animations, and even synchronizing multiple animations.
Examples of such libraries include:
GSAP (Greensock)anime.jsmo.jsVelocity.jsPopmotion
Always remember to optimize for performance because animations can cause a heavy load on the browser, which affects your website's performance. Use requestAnimationFrame where possible instead of setTimeout or setInterval.
Note: Not all styles can be animated. Only styles with numeric values can be animated, for example, you cannot animate an element's 'display' or 'background-image' property. For a full reference of what can and can't be animated, see this MDN Article: mdn.io/animate#animatable-css
It is important to also note that JavaScript animations are not always the best tool for the job. In some cases, CSS animations can provide smoother, less processor-intensive animations.
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