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JavaScript HTML DOM Animation
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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

My First JavaScript Animation

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Create an Animation Container
All animations should be relative to a container element.

Example

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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