Padding a string: left pad, right pad, repeating a string

str-pad.js

const rep = (str, n) => {
  if (n < 1 || !str) return '';
  let result = '';
  for (;;) {
    if (n & 1) {
      result += str;
    }
    n >>= 1;
    if (n < 1) break;
    str += str;
  }
  return result;
};

const leftPad = (str, n, value = ' ') => rep(value, n) + str;
const rightPad = (str, n, value = ' ') => str + rep(value, n);

const padWidthLeft = (str, width, value = ' ') =>
  str.length < width ? rep(value, width - str.length) + str : str;
const padWidthRight = (str, width, value = ' ') =>
  str.length < width ? str + rep(value, width - str.length) : str;

const repeatWidthLeft = (str, width) =>
  str ? rep(str, Math.floor(width / str.length)) + str.slice(0, width % str.length) : str;
const repeatWidthRight = (str, width) =>
  str ? str.slice(-(width % str.length)) + rep(str, Math.floor(width / str.length)) : str;

console.log('**********');
console.log(leftPad('abc', 7));
console.log(rightPad('abc', 7));
console.log(padWidthLeft('abc', 10, '-'));
console.log(padWidthRight('abc', 10, '-'));
console.log(repeatWidthLeft('abc', 10));
console.log(repeatWidthRight('abc', 10));
console.log(rep('*', 10));