Javascript DOM How to - Check element existance

Question

We would like to know how to check element existance.

Answer


<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'>
window.onload=function(){<!--   w ww .  j a  v  a 2s . c o  m-->
    if(document.getElementById('slider')){
        console.log("Id slider exist");
    }
    if(document.getElementsByClassName("someClass")[0]){
        console.log("Class exist");
    }
}
</script>
</head>
<body>
  <div id="slider"></div>
  <div class="someClass"></div>
</body>
</html>

The code above is rendered as follows: