Notice: This page requires JavaScript to function properly.
Please enable JavaScript in your browser settings or update your browser.
Aprenda Null vs Undefined | Data Types and Variables
Introduction to JavaScript

Deslize para mostrar o menu

book
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.

1
console.log(null === undefined);
copy

But null loosely equals undefined.

1
console.log(null == undefined)
copy

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.

Switch to desktopMude para o desktop para praticar no mundo realContinue de onde você está usando uma das opções abaixo
Tudo estava claro?

Como podemos melhorá-lo?

Obrigado pelo seu feedback!

Seção 3. Capítulo 32
single

single

Pergunte à IA

expand

Pergunte à IA

ChatGPT

Pergunte o que quiser ou experimente uma das perguntas sugeridas para iniciar nosso bate-papo

close

Awesome!

Completion rate improved to 2

book
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.

1
console.log(null === undefined);
copy

But null loosely equals undefined.

1
console.log(null == undefined)
copy

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.

Switch to desktopMude para o desktop para praticar no mundo realContinue de onde você está usando uma das opções abaixo
Tudo estava claro?

Como podemos melhorá-lo?

Obrigado pelo seu feedback!

close

Awesome!

Completion rate improved to 2

Deslize para mostrar o menu

some-alt