🔰iterable

an object that can iterate over itself.

JS ⟩ iteration ⟩ iterable

⭐️ ES6 (2015)

an object that can make iterators. (like Sequence in Swift, must implement .makeIterator() method)

for (const value of iterable) { ... }    // for-of
[...iterable]                 // spread into array elements
f(...iterable)                // spread into function arguments
const [a, b, c] = iterable;   // destructuring iterable
Array.from(iterable)          // iterable -> array

(by default) object is not iterable❗

let obj = { x: 1, y: 2, z: 3 };
for (let value of obj) { }                   // ⛔ TypeError

// ⭐️ workarounds
for (

👉 for-in vs. for-of vs. in

use cases：

for (const item of iterable) { ... } // ⭐️ for-of loop
[...iterable]                        // ⭐️ spread into array elements
f(...iterable)                       // ⭐️ spread into function arguments
let [a, b, c] = iterable

iterables：

, , , , ,
objects returned by s.
, object, ...
array., map., ...

must implement the named [].

some iterables ❗️

an iterable can be infinite. ( 👉 see： )

comforming to Iterable
- make-iterator method - method named [Symbol.iterator].
- Iterable+ext (extension) - extends iterables with custom methods.
- - check if an object is iterable.
iterable types
- / / /
💾 use cases
- for (const value of iterable) - loop.
special iterable
defining iterables
✨ ：
- - half-open range of numbers.
- - generate infinite iterable.

defining iterable (using generator function)

const iterable = {
    // ⭐️ "make-iterator" method
    *[Symbol.iterator]() {
        yield 1; yield 2; yield 3;
    },
};

more examples ...

*integers() - generate non-negative integers.
- sequence of numbers.

Previousobj.isIterable Nextmake-iterator method

Last updated 2 years ago

Was this helpful?

for (const value of iterable) { ... } // for-of [...iterable] // spread into array elements f(...iterable) // spread into function arguments const [a, b, c] = iterable; // destructuring iterable Array.from(iterable) // iterable -> array

for (const item of iterable) { ... } // ⭐️ for-of loop [...iterable] // ⭐️ spread into array elements f(...iterable) // ⭐️ spread into function arguments let [a, b, c] = iterable