Java Script Object Methods

<!DOCTYPE html>
<html>
<head>
<meta charset = "utf-8">
</head>
<body>
<h2>JavaScript Objects</h2>
<script>
var plane= {
  type:"MS", 
  model:2001, 
  color:"white"
}
document.write(Object.keys(plane).length);
</script>

</body>
</html>