I'm trying to get body tag attribute value in JavaScript. Here is body tag containing data-elementor-device-mode="tablet" attribute with value:

Here is the output when I call console.log in my browser console:

But when I write the same in my .js file I get null when call body.getAttribute('data-elementor-device-mode') or get undefined when call body.dataset.elementorDeviceMode.

Here is my code pieces:

const body = document.body
console.log(body.getAttribute('data-elementor-device-mode'))

const body = document.body
console.log(body.dataset.elementorDeviceMode)

Don't understand, what is problem. Can you help me please?