🍄object

reference types

JS ⟩ value ⟩ object

an unordered collection of properties (name : value pairs).

• inherits properties of another object, known as it's prototype.

• any value that is not primitive is an object.

// creating objects
{name: value}                        // object literal
new Object()                         // `new` statement
let obj = Object.create(prototype)   // specify an object's prototype

🈯 synonyms： "hash", "hashtable", "dictionary", "associated array".

⭐️ 重點

most common things to do with objects：

• create objects.

• access (get/set, delete / test / enumerate) their properties.

🔴 主題

• 🔰 creating objects

  • object literal / new / Object.create()

• 🔰 accessing properties

  • property access expression

    • dot notation (.) / bracket notation []

    • optional chaining (?., ?.[]) / optional invocation ?.()

  • delete / test / enumerate properties

• 🔰 extending objects

  • Object.assign() - copies properties from other objects.

  • mixin

  • inheritance

    • prototype

    • prototype chain

• 🔰 converting objects

  • serializing objects - convert/restore object's state to/from string.

  • .toString() / .toLacaleString() - object -> string.

  • .valueOf() - object -> primitive (typically a number)

  • .toJSON() - a method expected by JSON.stringify()

👥 相關

• use optional chaining (?., ?.[]) to safely acess object's members.

• literal

• event handler can be an object.

• the import in import.meta is NOT an object❗️

• JS object is associated array.

📗 參考

• ExploringJS ⟩ 14. New OOP features besides classes

• JavaScript: The Definitive Guide ⟩ Ch. 6 Object

📘 手冊

• MDN ⟩ JavaScript ⟩

  • JavaScript Guide ⟩ Working with objects

  • built-in objects ⟩

    • Object

    • Function

    • Proxy

🚧

• accessor property