Symbol iterator

The Symbol.

Iteration protocols aren't new built-ins or syntax, but protocols. These protocols can be implemented by any object by following some conventions. There are two protocols: The iterable protocol and the iterator protocol. The iterable protocol allows JavaScript objects to define or customize their iteration behavior, such as what values are looped over in a for Some built-in types are built-in iterables with a default iteration behavior, such as Array or Map , while other types such as Object are not. In order to be iterable , an object must implement the iterator method, meaning that the object or one of the objects up its prototype chain must have a property with a iterator key which is available via constant Symbol.

Symbol iterator

Help to translate the content of this tutorial to your language! Iterable objects are a generalization of arrays. Of course, Arrays are iterable. But there are many other built-in objects, that are iterable as well. For instance, strings are also iterable. For instance, we have an object that is not an array, but looks suitable for for.. To make the range object iterable and thus let for.. Technically, we may merge them and use range itself as the iterator to make the code simpler. Now range[Symbol. But two parallel for-ofs is a rare thing, even in async scenarios. Infinite iterators are also possible. For instance, the range becomes infinite for range. Or we can make an iterable object that generates an infinite sequence of pseudorandom numbers. Also can be useful. Of course, the for..

When you first research what an iterator is, you'll often come across vague definitions like this:.

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Summary : in this tutorial, you will learn about the JavaScript symbol primitive type and how to use the symbol effectively. ES6 added Symbol as a new primitive type. To create a new symbol, you use the global Symbol function as shown in this example:. The Symbol function accepts a description as an optional argument. The description argument will make your symbol more descriptive. The console.

Symbol iterator

The Symbol. The iterable protocol looks up this symbol for the method that returns the iterator for an object. In order for an object to be iterable, it must have an iterator key. Whenever an object needs to be iterated such as at the beginning of a for Some built-in types have a default iteration behavior, while other types such as Object do not. Some built-in types with a iterator method are:. See also Iteration protocols for more information. Or iterables can be defined directly inside a class or object using a computed property :.

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We can see that this key is actually a method:. What kind of Experience do you want to share? Data Analytics Data Analytics Course. It returns an iterator object that includes that special next method we mentioned above. CSS framework. Thank you for your valuable feedback! Add Other Experiences. You can use a for.. Now if we go back to the formal description of Symbol. Optionally, the iterator can also implement the return value and throw exception methods, which, when called, tells the iterator that the caller is done with iterating it and can perform any necessary cleanup such as closing database connection. Participate in Three 90 Challenge!

The Symbol. Used by for

As you can see, there's a big difference between these looping methods but Symbol. Now for the hardest definition of iterator. JavaScript Symbol description Property. Thank you for your valuable feedback! References Explore our selection of references covering all popular coding languages. If you can't understand something in the article — please elaborate. This can happen, for example, if a break or return is encountered in a for JavaScript Symbol search Property. Some built-in types are built-in iterables with a default iteration behavior, such as Array or Map , while other types such as Object are not. Solve Coding Problems.