Null vs Undefined

Similarities Between null and undefined

• Both are Falsy:
  A falsy (sometimes written falsey) value is a value that is considered as false when encountered in a Boolean context. There are six-falsy-value in JavaScript.

  • NaN (Not A Number)

  • 0 (Zero)

  • null

  • undefined

  • '' (empty string)

  • false
    Any value other than the above six falsy values, in JavaScript, will be considered as truthy.

• Both are Primitive Values:
  JavaScript has seven primitive values including null and undefined . Here is a full list:

  • Null

  • Undefined

  • String

  • Number

  • BigInt

  • Symbol

  • Boolean

null !== undefined:

Although null and undefined share some similarities but they are different from each other and it is obvious that the null and undefined are not strictly equal.

But null loosely equals undefined.

As we talk in the previous chapter == checks the loose equality. But In JavaScript, a double equals tests for loose equality and it performs type coercion. type coercion means converting the value to the common type. But === does not perform type type coercion.

Summary:

• The undefined variables are those variables that are declared without any values assigned to them.

• null is not assigned to a variable by default like the undefined .

• Both the null and undefined are falsy values.