Benchmark: Reverse a number

Tests:

reverseNum numerically
let num = 456 var r = 0; while (num) { r *= 10; r += num % 10; num = Math.floor(num / 10); } console.log(r)
The String way
let num = 456 Number(num.toString().split('').reverse().join('')) console.log(num)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reverseNum numerically
The String way

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.170 Safari/537.36

Browser/OS: Chrome 66 on Mac OS X 10.12.6

View result in a separate tab

Test name	Executions per second
reverseNum numerically	95212.2 Ops/sec
The String way	81251.7 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The provided benchmark definition represents two test cases: reversing a number using numerical methods and using strings to reverse the number.

*   The first test case, "reverseNum numerically," uses a while loop to extract each digit from the input number `num` by multiplying the current value of `r` by 10, adding the remainder of `num` divided by 10, and then updating `num` to be the integer division of the original `num` by 10. This process is repeated until there are no more digits left in `num`.
*   The second test case, "The String way," converts the input number to a string using `toString()`, splits the string into an array of characters, reverses the array using the `reverse()` method, and then joins the characters back together into a single string.

**Options Compared**

In this benchmark, we have two main options:

1.  **Numerical Method**: This approach uses a while loop to extract each digit from the input number.
2.  **String-Based Approach**: This approach converts the input number to a string and then reverses the string using the `reverse()` method.

**Pros and Cons of Each Approach**

*   **Numerical Method**
    *   Pros:
        *   More efficient for very large numbers, as it avoids the overhead of creating a new string.
        *   Less memory-intensive, as it only requires storing a single integer value (`r`).
    *   Cons:
        *   May be slower due to the use of a while loop and arithmetic operations.
*   **String-Based Approach**
    *   Pros:
        *   Can be faster for small numbers, as it avoids the overhead of arithmetic operations.
        *   Often more readable and easier to understand, especially for developers without deep knowledge of numerical algorithms.
    *   Cons:
        *   Less efficient for very large numbers due to the creation of a new string and the `reverse()` method.
        *   More memory-intensive, as it requires storing an additional string.

**Library Used**

In this benchmark, no libraries are explicitly mentioned. However, the `Number()` function used in the second test case is part of the JavaScript standard library.

**Special JS Feature or Syntax**

The use of arrow functions (`=>`) is not present in this benchmark. However, some other features like template literals (`\r\n`) and `let`/`const` declarations are used to define the script preparation code for each test case.

**Other Alternatives**

If you were to consider alternative approaches to reversing a number, here are a few options:

*   **Recursive Approach**: You could use recursion to reverse the number by calling a function with the last digit of `num` and incrementing `num` until there's only one digit left.
*   **Bit Manipulation**: For very large numbers, you could use bit manipulation techniques like bitwise XOR and shifts to extract each digit from the input number.
*   **BigInt**: If you're working with very large integers in modern JavaScript ( ECMAScript 2020 and later), you can use the `BigInt` type to represent arbitrary-precision integers.

Keep in mind that these alternative approaches might have their own trade-offs in terms of performance, readability, and memory usage.

Related benchmarks:

Reverse a number (version: 0)

Which is the faster way to reverse a number in JS?

Comparing performance of: reverseNum numerically vs The String way

Created: 6 years ago by: Guest

Jump to the latest result

reverseNum numerically

The String way

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):