🔸make-iterator method

JS⟩ iteration ⟩ iterable ⟩ make-iterator method

an iterable must implement a special method named [Symbol.iterator], which returns an iterator.

class A {
    // ⭐️ "make-iterator" method
    // make an iterator by using generator function.
    *[Symbol.iterator]() { yield 1; yield 2; }
}

⭐️ 重點

we can implement the make-iterator method by：

• returning iterator object directly ( 👉 see： ClosedRange)

• using generator function.

similar to .makeIterator() method of Sequence protocol in Swift

By default, using array[Symbol.iterator] will return the values() function.

do NOT use @@iterator as the method name, it's just a "specification" thing❗️

👥 相關

• [Symbol.iterator] is a computed property name.

✨ 範例

• Sequence - sequence of numbers.

• ClosedRange

📘 手冊

• Symbol.iterator ( = makeIterator in Swift )

• Swift ⟩ Sequence ⟩ .makeIterator()

• Array.prototype.values() - by default, arr[Symbol.iterator]() === arr.values()

• built-in types with a @@iterator method:

  • Array.prototype[@@iterator]()

  • TypedArray.prototype[@@iterator]()

  • String.prototype[@@iterator]()

  • Map.prototype[@@iterator]()

  • Set.prototype[@@iterator]()

🗣 討論

• ES 6: Difference between Symbol.iterator and @@iterator