How do I retrieve an HTML element's actual width and height?

Question

Suppose that I have a <div> that I wish to center in the browser's display (viewport). To do so, I need to calculate the width and height of the <div> element.

What should I use? Please include information on browser compatibility.

Answer 1

You should use the .offsetWidth and .offsetHeight properties. Note they belong to the element, not .style.

var width = document.getElementById('foo').offsetWidth;

Function .getBoundingClientRect() returns dimensions and location of element as floating-point numbers after performing CSS transforms.

> console.log(document.getElementById('id').getBoundingClientRect())
DOMRect {
 bottom: 177,
 height: 54.7,
 left: 278.5,
 right: 909.5,
 top: 122.3,
 width: 631,
 x: 278.5,
 y: 122.3,
}