Javascript data types, while null == undefined is true

javascript_data_type.js

// 0. Primitive data types (6): Boolean, Null, Undefined, String, Number, Symbol
//
// 1. Truely and Falsy value in javascript
// - Falsy (6 falsy value): false, 0, '' (empty string), null, undefined, NaN
// - Truely: All other values that differ 6 falsy value above.
//
// 2. Type Coerce
// - When checking equality (==) javascript will coerce operands to the same data type before compare.
// - With operator === javascript only compare operands when they are the same data type. Immediately return false when differ.
//
// 3. Type cast
// - String(), Number(), Boolean()
//
// 4. null and undefined
// - null has type object (this considered as an error in javascript), undefined has type undefined (typeof undefined)
// - null == undefined: return true because both is falsy values
// - null === undefined: returne false because null has type object while undefined has type undefined