Getting Name initials using JS

I would like to extract initials from a string, like:

Name = FirstName LastName 
Initials =  FL

I can get the above result using this,

const initials = item
    .FirstName
    .charAt(0)
    .toUpperCase() +
  
    item
    .LastName
    .charAt(0)
    .toUpperCase();

But now my requirements are changed as if name only consist of 1 word or more then 2, so in following cases how can I get initials as per my requirements,

FullName =  FU
FirstName MiddleName LastName = FL
1stName 2ndName 3rdName 4thName 5thName = 15

How can I get above initials from a string in JS?

Also now I only have item.Name string as an input

Why no love for regex?

Updated to support unicode characters and use ES6 features

let name = 'ÇFoo Bar 1Name too ÉLong';
let rgx = new RegExp(/(\p{L}{1})\p{L}+/, 'gu');

let initials = [...name.matchAll(rgx)] || [];

initials = (
  (initials.shift()?.[1] || '') + (initials.pop()?.[1] || '')
).toUpperCase();

console.log(initials);

You can use this shorthand js

"FirstName LastName".split(" ").map((n)=>n[0]).join(".");

To get only First name and Last name you can use this shorthand function

(fullname=>fullname.map((n, i)=>(i==0||i==fullname.length-1)&&n[0]).filter(n=>n).join(""))
("FirstName MiddleName OtherName LastName".split(" "));