Javascript Generator

Importance of Generator Function

Javascript Generator

Photo by Andrew Neel on Unsplash


Imagine you're trying to write a program that needs to process a large amount of data. You could do this using a regular function, but what if you only need to process part of the data at a time? Using a regular function would require you to load all of the data into memory at once, which could be slow and inefficient.

This is where generators come in. Generators allow you to create functions that can be paused and resumed during their execution, making them ideal for processing large amounts of data in smaller, manageable chunks. By using a generator function, you can load just a portion of the data into memory at a time, and then process it before moving on to the next chunk.

In addition to their use in data processing, generators can also be used to create iterators, coroutines, and asynchronous code in JavaScript. They provide a powerful and flexible mechanism for controlling the flow of execution in JavaScript programs and are an important tool for building complex applications.

Why Generators ??

Have you ever wondered why some programmers prefer to use generators instead of normal functions? While both can be used to accomplish similar tasks, there are some key differences that make generators a more powerful and flexible tool in certain situations.

Here are some of the benefits of using generators over normal functions:

  • Generators allow you to generate data on the fly, which can be more memory-efficient than loading all the data into memory at once.

  • They provide a way to handle asynchronous code more efficiently by pausing and resuming execution as needed.

  • Generators can provide an infinite source of data, which is useful in scenarios where you need to generate a large amount of data or simulate real-world scenarios.

  • They can make your code more readable and maintainable by breaking it down into smaller, more modular functions.

  • Generators can also reduce the amount of boilerplate code you need to write by encapsulating repetitive logic in a generator function.

  • Finally, generators can help you write more robust code by handling errors and exceptions more gracefully.

While normal functions have their uses, generators offer a more flexible and powerful tool for handling data and code in certain situations.


function* myGenerator() {
  // generator code goes here
  yield someValue;
  // more generator code goes here

Note :

  • The function* keyword is used to indicate that this is a generator function.

  • The function body contains one or more yield statements, which allow the generator to return a value and pause execution.

  • When called, a generator function returns a generator object, which can be used to iterate over the values yielded by the generator.


Simple example in which prime number generator function generates an infinite sequence of prime numbers.

Explanation :

In this example, the primeNumbers generator function generates an infinite sequence of prime numbers. It initializes a variable n to 2, and uses an infinite while loop to generate prime numbers. For each value of n, it checks whether it is prime by using a for loop to check whether it is divisible by any numbers between 2 and the square root of n. If n is prime, it yields n as the result of the generator function.

The primes variable is then initialized to a new instance of the primeNumbers generator function. We can use the next() method to iterate through the sequence of prime numbers. In this example, we use a for loop to print the first five prime numbers to the console, by calling for each iteration.

Using the yield keyword in the generator function allows us to create a sequence of prime numbers that is generated lazily, only computing the next prime number when it is needed. This can be more memory-efficient than computing all prime numbers up front and storing them in an array or other data structure.


In conclusion, generators are a powerful feature of JavaScript that allow us to write functions that can be paused and resumed at any point using the yield keyword. This makes it possible to create functions that can generate an infinite sequence of values, or that can perform long-running tasks without blocking the main thread of execution.

Generators are often used to implement lazy evaluation, where values are computed only when they are needed, rather than all at once up front. This can be especially useful when dealing with large datasets or computationally-intensive tasks, as it can help to conserve memory and improve performance.

In addition to the yield keyword, generators also provide the next() method, which allows us to iterate through the sequence of values generated by the generator function. We can also use the return() method to signal the end of the sequence, or the throw() method to raise an exception and stop the generator.

Overall, generators are a powerful tool in the JavaScript programmer's toolkit and can be used to solve a wide range of problems concisely and efficiently.

Here we come to the end of the blog thanks for reading it. I hope you enjoyed reading it. If you have any queries feel free to ask in the comment section :)