Can someone explain the purpose of 'yield' in JS?

Other Questions JavaScript
1

Hey everyone,

I’m trying to learn more about JavaScript and I keep coming across this thing called yield. It’s not something I’ve used before and I’m not really sure what it does. Can anyone break it down for me?

Here’s an example of what I’ve seen, but I don’t get it:

function* countToThree() {
  yield 1;
  yield 2;
  yield 3;
}

let counter = countToThree();
console.log(counter.next().value);

What’s going on here? Why use yield instead of just returning values? Any help would be awesome! Thanks in advance!

2

yield is pretty neat in JS! it’s like a pause button for functions. instead of spitting out everything at once, it lets u grab values one at a time. super handy for big data stuff or when u wanna make ur own custom loops. saves memory too!

3

The yield keyword in JavaScript is primarily used in generator functions. It allows you to pause and resume function execution, which is incredibly useful for managing asynchronous operations and creating iterables.

In your example, yield is used to produce a sequence of values one at a time. Each time next() is called on the generator, it runs until it hits a yield statement, then pauses and returns that value. This is different from a regular function that would run to completion and return all values at once.

This approach can be more memory-efficient for large datasets and provides a way to generate values on-demand, rather than computing everything upfront. It’s particularly useful in scenarios like processing large files or implementing custom iterators.

4

I’ve been using yield in my projects lately, and it’s been a game-changer. One practical application I found was in a web scraping task. Instead of loading all the data into memory at once, I used a generator function with yield to process the scraped data in chunks.

This approach significantly reduced memory usage and made the script more efficient, especially when dealing with large websites. It also allowed me to start processing data immediately, rather than waiting for the entire scrape to finish.

Another benefit I discovered is how yield simplifies writing iterators. Before, I’d have to implement a full iterator protocol, but now I can just use a generator function. It’s made my code cleaner and more maintainable.

Just remember, the learning curve can be a bit steep at first, but it’s worth it for certain scenarios.