How can I use a Math method to style an element?

I’m trying to give the element a random width of 1 – 100% but this isn’t working.

  document.querySelector(".box").style.width = Math.floor((Math.random() * 100) + 1)%;

>Solution :

You need to concatenate % as a string:

document.querySelector(".box").style.width = Math.floor((Math.random() * 100) + 1) + '%';