How does the Symbol.iterator work in JavaScript?

How does the Symbol.iterator work in JavaScript?

The Symbol.iterator is a built-in symbol that specifies the default iterator for an object. It allows objects to be iterable.

Can you give me an example of how to implement it?

Sure! You can implement it in a custom object like this:

const myIterable = {
  items: [1, 2, 3],
  [Symbol.iterator]() {
    let index = 0;
    return {
      next: () => {
        if (index < this.items.length) {
          return { value: this.items[index++], done: false };
        } else {
          return { done: true };
        }
      }
    };
  }
};

This allows you to use for...of loops on myIterable.

What are some use cases for Symbol.iterator?

Use cases include creating custom data structures, enabling for...of loops, and integrating with other iterable protocols like spread syntax.

Are there any performance considerations when using Symbol.iterator?

Yes, if your iterator performs complex calculations or accesses large data sets, it may impact performance. It's best to keep it efficient.