// siingle replace
"str".replace('s', 'a') // atr
"str".replace(/s|r/, 'a') //ata

// replace all occurrences
"strstr".replace(/s/, 'a') //atratr

// replace with a function
function replacer(match, p1, p2, p3, offset, string) {
  // p1 is nondigits, p2 digits, and p3 non-alphanumerics
  return [p1, p2, p3].join(' - ');
}
let newString = 'abc12345#$*%'.replace(/([^\d]*)(\d*)([^\w]*)/, replacer);
console.log(newString);  // abc - 12345 - #$*%