What am I doing wrong with .splice()

I'm just trying to get comfortable with .slice(), and .splice(). Why doesn't this code work? According to w3Schools .splice() takes 3 arguments, (index at which to begin adding/removing elements, # of elements to be removed, and what to add). Why does this function not work? P.S. Ignore they y, its just there as part of my experimenting.

let x = "Hello I like milk";
let y = ''

if(x[0] !== '(') {
 x = x.split(' ').splice(0, 0, '(');


}






console.log(x)