Justify strings to a given width. Works in-place without breaking the string into an array.

justify.js

function justify(str, width) {
  var whitespace = ' ';
  while (str.length < width) {
    var oldLength = str.length;
    var spacing = new RegExp("(\\w)" + whitespace + "(\\w)");
    str = str.replace(spacing, '$1 ' + whitespace + '$2');
    if (oldLength === str.length) {
      whitespace += ' ';
    }
  }
  return str
};

justify.rb

def justify!(str, width)
  whitespace = ' '
  while str.length < width
    spacing = Regexp.new("(\\w)#{whitespace}(\\w)")
    sub = str.sub!(spacing, "\\1 #{whitespace}\\2")
    whitespace << ' ' unless sub
  end
  str
end
  
def justify(str, width)
  justify!(str.dup, width)
end