Iterators and Iterables

links: YDK JS Chapter 3

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Let’s look at the interface of iterator and iterable to understand them clearly

“An object is an Iterable when it confirms to Iterable interface”

interface Iterable {
	[Symbol.iterator]() {
		// ...
		return Iterator;
	}
}

In simple words, any object is iterable (iter+able meaning able to be iterated) if it contains a method name Symbol.iterator (Symbols can also define methods) that returns an Iterator.

What’s an Iterator?

“The Iterator object must confirm to Iterator interface.”

The Iterator object must have a method next() that returns an object with properties done (a boolean indicating the end of the operation) and value (the item extracted from the collection at the iteration)

interface Iterator {
	next() {
		//...
		return {
			value: <value>,
			done: <boolean>
		}
	}
}

source

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tags: javascript , fundamentals