Detect whether the page is being viewed on a mobile device or a desktop

Use a regular expression to test the navigator.userAgent property to figure out if the device is a mobile device or a desktop.

const detectDeviceType = () =>
  /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(
    navigator.userAgent
  )
    ? 'Mobile'
    : 'Desktop';

// EXAMPLE
detectDeviceType(); // 'Mobile' or 'Desktop'

Source

https://www.30secondsofcode.org/js/s/detect-device-type