Science Knowings: JavaScript Course For Social Media

Iterator and Iterable Protocols

Moving to Iteration

Previously, we dove into Symbol Types, exploring their significance in JavaScript. Now, let's embark on a new adventure: understanding Iterators and Iterable Protocols!

Iterators and Iterables

Iterators and Iterables are two essential concepts that work together to provide a powerful mechanism for iterating over data collections.

Understanding Iterables

An iterable is any object that provides a way to access its elements sequentially. Arrays, strings, maps, and sets are all built-in examples of iterables.

Meet Iterators

An iterator is an object that represents a sequence. It provides a way to access the elements of an iterable object one at a time.

Why Use Iterators and Iterables?

Iterators and iterables simplify the traversal of data collections. They offer a clean and consistent way to work with sequences of elements.

Custom Iterators

Custom iterators allow you to define your own iteration logic. You can create an iterator for any data structure or object that needs to be iterated.

Creating Iterables

To make an object iterable, implement the Symbol.iterable method, which returns an iterator for the object.

Iterator Methods

next()Returns the next element in the sequence or done: true if the iteration is complete.
return()Stops the iteration and returns a specified value.
throw()Throws an exception and stops the iteration.

Iterable Methods

[Symbol.iterator]()Returns an iterator for the iterable object.

Key Differences


  • Represent a sequence of elements.
  • Provide a way to access elements sequentially.


  • Represent a stream of values.
  • Provide a way to access elements one at a time.

Real-World Applications

Iterators and iterables are essential for processing large and complex data sets. They are used in:

  • Looping over arrays
  • Iterating over DOM elements
  • Creating custom iterators for custom data structures

Introducing Generators

Are you ready to level up your iteration game? Our next topic, Generators, will empower you to create powerful and concise iterators.

Why Generators?

Generators allow you to create iterators and iterables in a more efficient way.

  • They offer lazy evaluation, yielding values only when needed.
  • They simplify the syntax for creating iterators.

Follow us to unravel the secrets of Generators!