JS
(quick guide & examples)
USE NULL TO EXPLICITLY DEFINE “NOTHING” OR “ABSENT”. var people = ["Jon", "Joy", null];
COMPARISON null == undefined TRUE null === undefined FALSE null == "" FALSE null === "" FALSE
OBJECT DATATYPE console.log(typeOf null);
A VARIABLE WITHOUT ASSIGNED VALUE var people;
COMPARISON undefined == null TRUE undefined === null FALSE undefined == "" FALSE undefined === "" FALSE
NO DATATYPE - UNDEFINED console.log(typeOf undefined);
AN EMPTY STRING var people = "";
COMPARISON "" == null FALSE "" === null FALSE "" == undefined FALSE "" === undefined FALSE
STRING DATATYPE console.log(typeOf "");
PUT "UNDEFINED" INTO ARRAY var people = ["Jon",];
PEOPLE[0] IS A STRING console.log(typeOf people[0]);
PEOPLE[1] IS UNDEFINED console.log(typeOf people[1]);