Is it possible to turn an entire webpage to grayscale using javascript

Question

I want my entire body tag to be at greyscale = 100% using javascript

like in css we can do it by using "*" selector

Answer 1

To select all elements, use * as well...

Array.from(document.getElementsByTagName("*"))
    .forEach(el => el.style.filter = 'grayscale(100%)');

However, if you just want to set grayscale on your page, use

document.body.style.filter = 'grayscale(100%)';

Answer 2

you can select entire body:

document.getElementsByTagName("BODY")[0];