In short
Objects that implement the iterator protocol (`.next()` returning `{value, done}`), the underlying mechanism that makes `for...of` and spread syntax work on arrays, strings, Maps and Sets. The iterator protocol provides a common abstraction for sequential consumption, which is why many built-in collections work with `for...of`, spread, and destructuring.
How to learn this
- 1Manually call `.next()` on an array's iterator (`arr[Symbol.iterator]()`). Validate your understanding by applying it in a small practical example.
- 2Implement a custom iterable object using `Symbol.iterator`. Validate your understanding by applying it in a small practical example.
- 3Understand how generators are a convenient shortcut for writing iterators.
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