Iterators in ECMAScript 2025 allow developers to process data lazily, avoiding memory issues associated with large or infinite datasets. An iterator is an object with a .next() method that, when called, returns a result object with value and done keys. To make an object iterable, it must implement a [Symbol.iterator]() method that returns an iterator, thus enabling use with for...of loops and the spread operator. This innovation provides a built-in solution for data processing that was previously reliant on generator functions or external libraries.
Iterators are built exactly for scenarios where processing data lazily is essential, avoiding loading everything into memory, thus preventing memory overload and application crashes.
Until now, JavaScript developers relied on generator functions or third-party libraries to achieve lazy processing of data, but ECMAScript 2025 introduces built-in iterator helper methods.
Iterators produce values one at a time through the .next() method, returning a result object that indicates whether more values are available.
An iterable is defined by having a [Symbol.iterator]() method that returns an iterator, thus supporting constructs like for...of and Array.from().
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