Functional string spliter

index.js

const curry = require('lodash/curry');

const spliter = curry((separateTo,sign,string) => {
  string = string.split('');
  return string.reduce((comb,current,i) => 
    ((i+1) % separateTo === 0 && (i + 1) !== string.length) 
      ? comb + current + sign
      : comb + current
)});

let cardNumber = "6037224422442244";
const fourSpliter = spliter(4);
console.log(fourSpliter(":)",cardNumber)); // 6037:)2244:)2244:)2244