How can I insert a character after every n characters in javascript?

I have a string: "The quick brown fox jumps over the lazy dogs."

I want to use JavaScript (possibly with jQuery) to insert a character every n characters. For example I want to call:

var s = "The quick brown fox jumps over the lazy dogs.";
var new_s = UpdateString("$",5);
// new_s should equal "The q$uick $brown$ fox $jumps$ over$ the $lazy $dogs.$"

The goal is to use this function to insert ­ into long strings to allow them to wrap.

Maybe someone knows of a better way?

With regex

"The quick brown fox jumps over the lazy dogs.".replace(/(.{5})/g,"$1$")

The q$uick $brown$ fox $jumps$ over$ the $lazy $dogs.$

cheers,

function chunk(str, n) {
    var ret = [];
    var i;
    var len;

    for(i = 0, len = str.length; i < len; i += n) {
       ret.push(str.substr(i, n))
    }

    return ret
};

chunk("The quick brown fox jumps over the lazy dogs.", 5).join('$');
// "The q$uick $brown$ fox $jumps$ over$ the $lazy $dogs."

> Keep it simple

  var str = "123456789";
  var parts = str.match(/.{1,3}/g);
  var new_value = parts.join("-"); //returns 123-456-789

let s = 'The quick brown fox jumps over the lazy dogs.';
s.split('').reduce((a, e, i)=> a + e + (i % 5 === 4 ? '$' : ''), '');

Explain: split('') turns a string into an array. Now we want to turn the array back to one single string. Reduce is perfect in this scenario. Array's reduce function takes 3 parameters, first is the accumulator, second is the iterated element, and the third is the index. Since the array index is 0 based, to insert after 5th, we are looking at index i%5 === 4.

var str="ABCDEFGHIJKLMNOPQR";
function formatStr(str, n) {
   var a = [], start=0;
   while(start<str.length) {
      a.push(str.slice(start, start+n));
      start+=n;
   }
   console.log(a.join(" "));
}
formatStr(str,3);

function addItemEvery (str, item, every){
  for(let i = 0; i < str.length; i++){
    if(!(i % (every + 1))){
      str = str.substring(0, i) + item + str.substring(i);
    }
   }
  return str.substring(1);
}

Result:

> addItemEvery("The quick brown fox jumps over the lazy dogs.", '$', 5)
> "The q$uick $brown$ fox $jumps$ over$ the $lazy $dogs."

Here's one of the previous answers, but I wrapped it in a function, and I gave it an "offset" parameter instead of hard coding it.

// https://stackoverflow.com/a/2712896/3480193
addCharToStringEveryXSpots(str, char, offset) {
	if ( ! char ) {
		return str;
	}
	
	let regExPattern = new RegExp('(.{' + offset + '})', 'g');
	
	return str.replace(regExPattern, '$1' + char);
};

I did something similar to separate a friendCode for a mobile app but using Array and reduce.

This will take a string, check every n characters and add delimiter at that location.

/**
 * A function to easily inject characters every 'n' spaces
 * @param {string} friendCode The string we want to inject characters in
 * @param {*} numDigits Determines the 'n' spaces we want to inject at
 * @param {*} delimiter The character(s) we want to inject
 */
function formatFriendCode(friendCode, numDigits, delimiter) {
  return Array.from(friendCode).reduce((accum, cur, idx) => {
    return accum += (idx + 1) % numDigits === 0 ? cur + delimiter : cur;
  }, '')
}

formatFriendCode("000011112222", 4, ' ')
// output "0000 1111 2222 "

formatFriendCode("The quick brown fox jumps over the lazy dogs.", 5, '$')
// output "The q$uick $brown$ fox $jumps$ over$ the $lazy $dogs.$"