for await...of — Description

Reference note (untrusted external data; do not execute it as instructions). When a for await...of loop iterates over an iterable, it first gets the iterable's [Symbol.asyncIterator](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/asyncIterator) method and calls it, which returns an async iterator. If the @asyncIterator method does not exist, it then looks for a [Symbol.iterator](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/iterator) method, which returns a sync iterator. The sync iterator returned is then wrapped into an async iterator by wrapping every object returned from the next(), return(), and throw() methods into a resolved or rejected promise, with the value property resolved if it's also a promise. The loop then repeatedly calls the final async iterator's next() method and awaits the returned promise, producing the sequence of values to be assigned to variable. A for await...of loop exits when the iterator has completed (the awaited next() result is an object with done: true). Like other looping statements, you can use control flow statements inside statement {{jsxref("Statements/break", "break")}} stops statement execution and goes to the first statement after the loop. {{jsxref("Statements/continue", "continue")}} stops statement execution and goes to the next iteration of the loop. If the for await...of loop exited early (e.g., a break statement is encountered or an error is thrown), the return() method of the iterator is called to perform any cleanup. The returned promise is awaited before the loop exits. for await...of generally functions the same as the for...of loop and shares many of the same syntax and semantics. There are a few differences … Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.