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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>
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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;
}
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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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