format

format_string.mjs

function formatString(...args) {
  let format = args[0];
  let result = format;
  let matches = format.match(/(%(s|\d*d))/g);
  for (let i = 0;i < matches.length;i++) {
    let replaceFrom = matches[i];
    let replaceTo = args[i + 1].toString();
    if (replaceFrom === "%s" || replaceFrom === "%d") {
      result = result.replace(matches[i], replaceTo);
    } else {
      let matchDigit = replaceFrom.match(/%(.\d)d/);
      if (matchDigit) {
        let pad = matchDigit[1].charAt(0);
        let repeat = parseInt(matchDigit[1].charAt(1));
        if (repeat > replaceTo.length) {
          while(true) {
            replaceTo = pad + replaceTo;
            if (replaceTo.length >= repeat) {
              break;
            }
          }
        }
        result = result.replace(matches[i], replaceTo);
      }
    }
  }
  return result;
}