JavaScript
HTML DOM Animation
Learn to
create HTML animations using JavaScript.
A Basic Web
Page
To
demonstrate how to create HTML animations with JavaScript, we will use a simple
web page:
Example
<!DOCTYPE
html>
<html>
<body>
<h1>My
First JavaScript Animation</h1>
<div
id="animation">My animation will go here</div>
</body>
</html>
»
Create an
Animation Container
All
animations should be relative to a container element.
Example
<div
id ="container">
<div id ="animate">My
animation will go here</div>
</div>
Style the
Elements
The
container element should be created with style = "position:
relative".
The
animation element should be created with style = "position:
absolute".
Example
#container
{
width: 400px;
height: 400px;
position: relative;
background: yellow;
}
#animate
{
width: 50px;
height: 50px;
position: absolute;
background: red;
}
»
Animation
Code
JavaScript
animations are done by programming gradual changes in an element's style.
The changes
are called by a timer. When the timer interval is small, the animation looks
continuous.
The basic
code is:
Example
var
id = setInterval(frame, 5);
function
frame() {
if (/* test for finished */) {
clearInterval(id);
} else {
/* code to change the element style
*/
}
}
Create
the Animation Using JavaScript
Example
function
myMove() {
var elem =
document.getElementById("animate");
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';
}
}
}
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