Скачать или смотреть Understanding Why the Factorial Function Returns 120 Instead of 1

Dive into the workings of the factorial function in JavaScript, discovering how recursion leads to a result of 120. Learn about base cases and recursive calls in simple terms.
---
This video is based on the question https://stackoverflow.com/q/74678389/ asked by the user 'll Web Style ll' ( https://stackoverflow.com/u/20478727/ ) and on the answer https://stackoverflow.com/a/74678448/ provided by the user 'Aurast' ( https://stackoverflow.com/u/3298338/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Why factorial function return not 1?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Why the Factorial Function Returns 120 Instead of 1

When we delve into programming, certain concepts can be perplexing—like understanding how a function can yield a number like 120 when you expect it may return just 1. The factorial function in JavaScript is one of those fascinating examples. If you’ve ever asked yourself, “Why does the factorial function return not 1?” you’re in the right place! In this post, we’ll unravel the mystery of the factorial function, explain the recursion behind it, and clarify how it reaches its final result.

What is the Factorial Function?

The factorial function, denoted as n!, calculates the product of all positive integers from n down to 1. For instance:

5! = 5 × 4 × 3 × 2 × 1 = 120

4! = 4 × 3 × 2 × 1 = 24

In this case, when we call the function with 5, we can expect it to compute 5!.

Analyzing the Code

Here’s a straightforward implementation of the factorial function in JavaScript:

[[See Video to Reveal this Text or Code Snippet]]

Let’s break this down step-by-step to clarify why the function does not return 1.

Understanding Recursion

The key to grasping the factorial function lies in the concept of recursion—a method where the function calls itself to break down a problem into smaller chunks.

Initial Call: When factorial(5) is called, the check n != 1 passes. Therefore, JavaScript executes 5 * factorial(4).

Subsequent Calls: This pattern continues:

factorial(4) calls 4 * factorial(3)

factorial(3) calls 3 * factorial(2)

factorial(2) calls 2 * factorial(1)

Base Case: The recursion reaches its base case when factorial(1) is called, and it returns 1.

Now, the execution starts to unravel:

Unraveling the Recursion

Once the base case has been reached, the function begins to return values back up the call stack:

factorial(1) returns 1.

factorial(2) calculates 2 * 1 = 2 and returns 2.

factorial(3) computes 3 * 2 = 6 and returns 6.

factorial(4) evaluates 4 * 6 = 24 and returns 24.

Finally, factorial(5) computes 5 * 24 = 120 and returns 120.

Conclusion

So, there you have it! The reason the factorial function does not return 1 when you call it with 5 is due to the recursive nature of the function and the sequence of calculations that occur. Each level of recursion builds on the previous ones, ultimately leading to the final product of 5!, which is 120.

Understanding recursion can open up a new world of programming possibilities, so don’t hesitate to take the time to explore it further. Happy coding!