code: function getInputExcerpt(input, pos, len) {
    var excerpt = asEscapedString(input.slice(pos, pos + len));
  
    // Pad the output if necessary.
    if (excerpt.length < len) {
      return excerpt + common.repeat(' ', len - excerpt.length).join('');
    }
    return excerpt;
  }
docs: Return a string representation of a portion of `input` at offset `pos`. The result will contain exactly `len` characters.