Sample code in Google Apps Script

function myFunction(n) {
  Logger.log(n); /* expected output: "n" */
  Logger.log(n.length) /* expected output: 1 */
  return n;
}

Logger.log(myFunction("n")); /* expected output: "n" */

Execution log

21.35.48    Info    n
21.35.48    Info    1.0
21.35.48    Info    n
21.35.48    Info    null
21.35.48    Error   TypeError: Cannot read property 'length' of undefined myFunction @ Test.gs:3

Granted I come from a Python background and this is my first project in Javascript, however I don't have a single idea on why the log shows TypeError. In my project, I can't read the length of 'n' and always quits with error.

Any help is much appreciated!