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Iterable object (iterable)

An iterable object (iterable) is an object with Symbol.iterator deployed. The return value of the iterator is automatically obtained when traversing with for-of

const obj = {
  [Symbol.iterator]: function*() {
    for (let i = 9; i > 0; i--) yield i

for (let i of obj) {

Determine whether an object is traverable or not

is to see if the Symbol.iterator interface is deployed. This property is of type function.

function isIterable(obj) {
  return typeof obj[Symbol.iterator] === "function"

Js built-in iterable

String, Array, Map, Set, arguments and other pseudo arrays, generator

Note that WeakMap and WeakSet are not iterable

console.log(isIterable("")) // true
console.log(isIterable([])) // true
console.log(isIterable(new Map())) // true
console.log(isIterable(new WeakMap())) // false
console.log(isIterable(new Set())) // true
console.log(isIterable(new WeakSet())) // false
console.log(isIterable(arguments)) // true
console.log(isIterable(document.getElementsByTagName("script"))) // true
console.log(isIterable((function*() {})())) // true

FileList is also a pseudo array