How to double every character in a string?

Question

JavaScript

How to make a doubling of each character?

For example: Ihor-> IIhhoorr.

Answer 1

''.concat(...Array.from(str, n => n.repeat(2)))
or or or or
str.replace(/./g, '$&$&')
str.replace(/./g, m => Array(3).join(m))
[...str].flatMap(n => Array(2).fill(n)).join('')
str.split('').reduce((acc, n) => acc + n + n, '')