Iterable protocol
The iterable protocol is the JavaScript protocol by which an object provides a method keyed by Symbol.iterator that returns an iterator.
The Joy of JavaScript
Symbol.iterator is a built-in JavaScript symbol that defines the method an object uses to provide its iterator.
- How it is used
- Customizes how objects participate in for...of loops, spread expressions, and destructuring.
- How deep it goes
- Defines Symbol.iterator, iterator results, delegation, and generators, while deferring detailed generator and asynchronous treatment.
- Examples
- Uses strings, Blockchain, Block, Transaction, Pair, and Validation to demonstrate delegation, termination, generators, and destructuring.
- What you can do after
- Apply it via JavaScript to build custom objects that work with standard iteration syntax and composable data-processing patterns.
Get Programming with JavaScript Next: New features of ECMAScript 2015, 2016, and beyond
The well-known property name that an iterable object exposes to supply an iterator in JavaScript.
- How it is used
- Enables objects to supply values to `for...of` and spread through a common protocol.
- How deep it goes
- Explains the `Symbol.iterator` method, `next()` results, and completion, then demonstrates manual and generator-based implementations.
- Examples
- Uses array indices versus values, a three-prime iterable, a customized string iterator, and a bounded-iteration exercise.
- What you can do after
- Build it from scratch by supplying `Symbol.iterator`, or customize an existing iterable’s yielded values.
Related concepts
- iterableused by · An iterable is an object or value that provides or supports a protocol for producing its elements sequentially.
- Validationimplemented by · Validation is a computation or value type representing either a successful result or failure information while supporting successful processing and failure propagation or accumulation.
- destructuring assignmentused by · Destructuring assignment is syntax that decomposes a structured value according to a pattern and binds selected components to names.
- value propertyproduces · The value property is the field of an iterator result object that contains the item produced for the current iteration step.
- doneproduces · done is a Boolean property of an iterator result that indicates whether the iterator has finished producing values.
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