Javascript insert space at nth position in string

Question

Let's say I have the following string: "Stackoverflow", and I want to insert a space between every third number like this: "S tac kov erf low" starting from the end. Can this be done with regexes?

I have done it the following way with a for-loop now:

var splitChars = (inputString: string) => {
    let ret = [];
    let counter = 0;
    for(let i = inputString.length; i >= 0;  i --) {
       if(counter < 4) ret.unshift(inputString.charAt(i));
       if(counter > 3){
        ret.unshift(" ");
        counter = 0;
        ret.unshift(inputString.charAt(i));
        counter ++;
       } 
       counter ++;
    }
    return ret;
}

Can I shorten this is some way?

Answer 1

You could take a positive lookahead and add spaces.

console.log("StackOverflow".replace(/.{1,3}(?=(.{3})+$)/g, '$& '));