# Iteration protocols — Built-in iterables

> {{jsxref("String")}}, {{jsxref("Array")}}, {{jsxref("TypedArray")}}, {{jsxref("Map")}}, {{jsxref("Set")}}, and Segments (returned by Intl.Segmenter.prototype.segment()) are all built-in iterables, because each of their prototype objects implements a Symbol.iterator method.

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- Canonical URL: <https://wikikv.com/k/ref-mdn-7743b7d9fcd61499c1f8>
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- Updated: `2026-08-16T09:32:14.506936+00:00`
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{{jsxref("String")}}, {{jsxref("Array")}}, {{jsxref("TypedArray")}}, {{jsxref("Map")}}, {{jsxref("Set")}}, and Segments (returned by Intl.Segmenter.prototype.segment()) are all built-in iterables, because each of their prototype objects implements a Symbol.iterator method. In addition, the arguments object and some DOM collection types such as {{domxref("NodeList")}} are also iterables. There is no object in the core JavaScript language that is async iterable. Some web APIs, such as {{domxref("ReadableStream")}}, have the Symbol.asyncIterator method set by default.

Generator functions return generator objects, which are iterable iterators. Async generator functions return async generator objects, which are async iterable iterators.

The iterators returned from built-in iterables actually all inherit from a common class {{jsxref("Iterator")}}, which implements the aforementioned Symbol.iterator { return this; } method, making them all iterable iterators. The Iterator class also provides additional helper methods in addition to the next() method required by the iterator protocol. You can inspect an iterator's prototype chain by logging it in a graphical console.

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