How to get the accent/diacritic of a letter in javascript?

I want to get the accent/diacritic of a letter in javascript.

For example:

• ñ -> ~
• á -> ´
• è -> `

I tried using .normalize("NFD") but it doesn't return the correct accent/diacritc

string = "á"
string.normalize("NFD").split("")
// ['a', '́']
string.normalize("NFD").split("").includes("´") 
// false
'́' === "´"
// false

from How to get the accent/diacritic of a letter in javascript?