How to display an array with nested arrays in one line, without commas?

Question

JavaScript

let array = [
    ["1", "2"],
    "3",
    ["4",  ["5", "6"] ]
]

alert(array.toString())
// 1, 2, 3, 4, 5, 6

alert(array.join(''))
// 1, 2 3 4, 5, 6
// А нужно: 1 2 3 4 5 6

I need the simplest possible way to display an array and its nested arrays in one line without commas. toString prints with commas, Join doesn't work with nested arrays

Answer 1

const array = [
    ["1", "2"],
    "3",
    ["4",  ["5", "6"], ["7", "8"] ],
    ["9", "10", ["11", "42"]]
]

const res = array.flat(Infinity).join(" ");
console.log(res);