Un(in)dents a block of text (removing unwanted whitespace at the beginning of a line, but preserving desired indentation)

undentBlock.js

function undentBlock(block) {
  let REGEX_INDEX = /^[ \t]*\**[ \t]+/g;
  let indent = null;
  block.split("\n").forEach(function (line) {
    let match = line.match(REGEX_INDEX);
    let cur = match !== null ? match[0].replace(/\*/g, "").length : null;
    if (cur < indent || indent === null) indent = cur;
  });
  let ret = "";
  block.split("\n").forEach(function (line) {
    line = undent(line, indent);
    ret += line;
  });
  return ret;
}

function undent(str, remove) {
  let ret = "";
  let count = 0;
  for (var i = 0; i < str.length; i++) {
    let c = str.charAt(i);
    if ((c === " " || c === "*") && count <= remove) {
      count++;
    } else {
      break;
    }
  }
  ret = str.substr(count, str.length);
  if (ret === "\n" || ret === " ") ret;
  return ret + "\n";
}