Benchmark: index vs lastindexoft

Tests:

lastIndexOf
let str = 'Hello, World!'; let reverseStr = str.split('').reverse().join(''); let n = reverseStr.indexOf('hello');
indexOf
let str = 'Hello, World!'; let n = str.indexOf('hello');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lastIndexOf
indexOf

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/114.0

Browser/OS: Firefox 114 on Windows

View result in a separate tab

Test name	Executions per second
lastIndexOf	3214100.0 Ops/sec
indexOf	529630336.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the explanation into smaller parts to make it easier to understand.

**Benchmark Definition**

The provided JSON represents a JavaScript microbenchmark, which is a small piece of code designed to measure the performance of specific JavaScript features or libraries.

In this case, there are two benchmark definitions:

1. "index vs lastindexoft"
2. Two individual test cases: "lastIndexOf" and "indexOf"

**Options Compared**

The first benchmark definition, "index vs lastindexoft", compares two different approaches to find the last index of a substring in a string.

- **LastIndexOf**: This method returns the highest index of the specified value, within the bounds of the string. It uses a linear search approach.
- **LastIndexOf**: This method returns the lowest index of the specified value, within the bounds of the string. It also uses a linear search approach.

**Pros and Cons**

Both LastIndexOf and indexOf methods have their own advantages and disadvantages:

*   **Advantages:**
    *   They are implemented in native code (not JavaScript), making them faster than pure JavaScript implementations.
    *   They can handle large strings efficiently without consuming excessive memory.
*   **Disadvantages:**
    *   They only work on the client-side of web applications and do not support all JavaScript environments.
    *   They can be less readable than pure JavaScript solutions.

**Library and Special JS Feature**

There are no libraries used in these benchmarks, but note that `join()` function is used in both benchmark definitions. The `join()` method concatenates an array of strings into a single string, with the string it's called on as the separator between each string.

If you were to use this code outside of MeasureThat.net or if you wanted more robust handling for edge cases (e.g., null or undefined input), consider using modern JavaScript features like `reduce()` instead of `join()`:

```javascript
let str = 'Hello, World!';
let reverseStr = Array.from(str).reverse().join('');
```

**Other Alternatives**

If you needed to find the last index of a substring in a string for a specific requirement that wasn't covered by LastIndexOf or indexOf methods, some alternatives could be using regular expressions:

```javascript
let str = 'Hello, World!';
let regex = new RegExp('hello', 'gi');
let lastIndex = str.lastIndexOf(regex);
```

Or perhaps implementing your own solution in JavaScript without relying on the built-in methods. Keep in mind that this would likely result in slower performance and could be more code to write.

```javascript
function lastIndexOf(str, substr) {
    for (let i = 0; i < str.length; i++) {
        if (str.substr(i, substr.length) === substr) return i;
    }
    return -1;
}

let str = 'Hello, World!';
let index = lastIndexOf(str, 'hello');
```

**Conclusion**

MeasureThat.net allows developers to create and run JavaScript microbenchmarks on various browsers and devices. The provided benchmark definition compares the performance of two different approaches to find the last index of a substring in a string using LastIndexOf and indexOf methods. It's essential to consider factors like performance, readability, and compatibility when selecting an approach for real-world applications.

Related benchmarks:

index vs lastindexoft (version: 0)

Comparing performance of: lastIndexOf vs indexOf

Created: one year ago by: Guest

Jump to the latest result

lastIndexOf

indexOf

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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