Benchmark: index vs lastindexof

Tests:

lastIndexOf
var str = "Hello world, welcome to the universe."; var n = str.lastIndexOf("welcome");
indexOf
var str = "Hello world, welcome to the universe."; var n = str.indexOf("welcome");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lastIndexOf
indexOf

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

Measuring the performance of different approaches to search for a substring in a string is an interesting benchmark. The provided JSON represents two test cases:

**Benchmark Definition**
```json
{
    "Name": "index vs lastindexof",
    "Description": null,
    "Script Preparation Code": null,
    "Html Preparation Code": null
}
```
This defines the overall benchmark, which consists of only one test case. The script preparation code and HTML preparation code are empty, indicating that no additional setup is required for these tests.

**Individual Test Cases**
```json
[
    {
        "Benchmark Definition": "var str = \"Hello world, welcome to the universe.\";\r\nvar n = str.lastIndexOf(\"welcome\");",
        "Test Name": "lastIndexOf"
    },
    {
        "Benchmark Definition": "var str = \"Hello world, welcome to the universe.\";\r\nvar n = str.indexOf(\"welcome\");",
        "Test Name": "indexOf"
    }
]
```
These two test cases are identical, except for the method used to search for the substring. The first test case uses `lastIndexOf`, while the second test case uses `indexOf`. Both tests take a string and a substring as input.

**Options Compared**

The two options being compared are:

1. **`lastIndexOf()`**: This method returns the highest index of the specified value, or -1 if the value is not found.
2. **`indexOf()`**: This method returns the lowest index of the specified value, or -1 if the value is not found.

**Pros and Cons**

* `lastIndexOf()`: Pros:
	+ Can be faster for searching from the end of the string.
	+ Less prone to edge cases (e.g., no substring found).
Cons:
	+ May use more memory or CPU cycles due to its algorithmic complexity.
* `indexOf()`**: Pros:
	+ Generally faster and more efficient.
	+ Easier to implement, with less overhead.
Cons:
	+ Can return incorrect results if the search starts from an invalid position.

**Library/Feature**

In this benchmark, no libraries are used. The tests only rely on built-in JavaScript methods: `lastIndexOf()` and `indexOf()`. These methods are part of the ECMAScript standard, so they are supported by most modern browsers and environments.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax mentioned in this benchmark. The code snippets use basic string manipulation and variable declarations, which are widely supported across different JavaScript engines.

**Other Alternatives**

Some other alternatives to `lastIndexOf()` and `indexOf()` might include:

* Using regular expressions (e.g., `/welcome/g`) for more complex substring matching.
* Implementing custom search algorithms or data structures (e.g., suffix trees) for specific use cases.
* Utilizing browser-specific APIs or extensions (e.g., WebAssembly, SIMD instructions) to optimize performance.

Keep in mind that these alternatives might not be supported by all JavaScript engines or browsers, and may require additional setup or implementation.

Latest run results:

Run details: (Test run date: 2 days ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Linux

View result in a separate tab

Test name	Executions per second
lastIndexOf	55164080.0 Ops/sec
indexOf	240776464.0 Ops/sec

Related benchmarks:

index vs lastindexof (version: 0)

Comparing performance of: lastIndexOf vs indexOf

Created: 6 years 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 27 days ago):