📦primary expression

the simplest expressions. (literal, keyword, variable, global object property)

JS ⟩ statement ⟩ expression ⟩ primary

an expression that doesn't include any simpler expressions, they are：

• literal (object/array literal not included, MDN includes these!)

• keyword (some of them, not all)

• RHS reference to variable / global object property

// examples
123          // ⭐️ literal
null         // ⭐️ keyword (reference)
name         // ⭐️ variable (reference)
undefined    // ❗️ global object property (reference)

🔴 主題

• primiary expressions (listed in MDN)

  • this - property of execution context (environment record, actually).

  • function - defines a function expression.

  • class - defines a class expression.

  • function* defines a generator function expression.

  • yield pause and resume a generator function.

  • yield* delegate to another generator function or iterable object.

  • async function defines an async function expression.

  • await - wait for the promise's future value.

  • async function* define an async generator function expression.

  • array literal - []

  • object literal - {}

  • /ab+c/i regular expression literal syntax.

  • ( ) grouping operator.

👥 相關

• literal / keyword / variable / global object property

⭐️ 重點

you can use an expression to refer to an object's property.

👉 bracket notation []

📗 參考

• JavaScript: The Definitive Guide ⟩

  • 1.3 A Tour of JavaScript

  • Ch. 4：Expressions & Operators

• Expressions versus statements in JavaScript ⭐️

• Javascript 的表達式 (Expressions) 和陳述式 (Statements)：一個用說的，一個用做的

📘 手冊

• Expressions and operators ⟩ Primary Expressions