javascript - When are some css styles added using string objects generally used?

Question

var cs = "hello world!";
document.write(cs.fontcolor("red"));

It feels like it’s rarely used, right?

Answer 1

Basically it will not be used. Nowadays, whoever develops does not use a framework, so the underlying functions will be less used.

Answer 2

js splicing html code

Answer 3

I’ve never seen this usage before. Isn’t it all about adding classes to DOM elements? 9