Javascript : How to get width and height of a div?

Problem :

You have a <div> and you want to get the dimension of the <div> such as height and width. You want to ensure that the <div> dimension is not being tempered by third-party browser's add-ons.

How to do that?

Solution :

Imagine you have a <div id="box"> with id = box. You can get the dimension with getElementById() function to get the offsetWidth and offsetHeight properties.

For example :

the HTML :

 <div id="box">
 fill up something here
 the more you fill... the higher
 the height will be
 <br>
 <br>

 </div>

and the Javascript :

 var element = document.getElementById('box');
 var height = element.offsetHeight;
 alert(height);

 var width = element.offsetWidth;
 //alert(width)

See demo at http://codepen.io/anon/pen/KdVXLw

IF the height or width is below certain pixels, you can either prompt alert to your website visitors or redirect them to another page.