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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>

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

id = setInterval(frame, 5);

function frame() {
  if (/* test for finished */) {
    clearInterval(id);
  } else {
    /* code to change the element style */ 
  }
}

Create the Full Animation Using JavaScript

Example

function myMove() {
  let id = null;
  const elem = document.getElementById("animate");
  let pos = 0;
  clearInterval(id);
  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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