Benchmark: index vs lastindexof empty with startIndex set to 0

Tests:

lastIndexOf
var str = "According to that, indexOf is just a little bit faster. Of course, it does depend on what you are indexing.IndexOf looks for the first occurrence and lastIndexOf returns to the last occurrence. That all said, their are much better functions around now like map.To be honest though, if Google is using it there is probably a good reason."; var n = str.lastIndexOf("havent string", 0);
indexOf
var str = "According to that, indexOf is just a little bit faster. Of course, it does depend on what you are indexing.IndexOf looks for the first occurrence and lastIndexOf returns to the last occurrence. That all said, their are much better functions around now like map.To be honest though, if Google is using it there is probably a good reason."; var n = str.indexOf("havent string", 0);

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 gemma2:9b, generated 27 days ago):

LLMs can make mistakes. Check important info.

This benchmark compares the performance of two JavaScript string methods: `indexOf()` and `lastIndexOf()`.

**What's being tested?**

The benchmark measures how many times each method can successfully find a specific substring within a larger string in a given amount of time. The substring is "havent string", and both tests use `startIndex` set to 0.

* **`indexOf()`:** This method returns the *first* occurrence of the substring within the string, starting from the specified index (in this case, 0).
* **`lastIndexOf()`:** This method returns the *last* occurrence of the substring within the string, starting from the specified index (again, 0 in this case).

**Options Compared:**

The benchmark directly compares `indexOf()` and `lastIndexOf()`.  It doesn't offer alternative libraries or approaches because it focuses on built-in JavaScript functionality.

**Pros and Cons:**

* **`indexOf()`:**
    * **Pro:** Generally faster than `lastIndexOf()` when searching for the first occurrence of a substring. 
    * **Con:** Returns -1 if the substring is not found, which can require additional checks in your code.
* **`lastIndexOf()`:**
    * **Pro:** Useful when you need to find the last occurrence of a substring, especially towards the end of the string.
    * **Con:** Typically slower than `indexOf()` because it needs to scan the entire string backward.

**Alternatives:**
While not explored in this benchmark, alternative methods for finding substrings include:

* **Regular Expressions (`RegExp`):** Offer more complex pattern matching capabilities but can be slower than built-in string methods for simple searches.
* **Third-party Libraries:** Some libraries, like Lodash or Underscore.js, provide optimized string manipulation functions that might offer performance improvements in certain scenarios.

**Key Considerations:**

* **String Length:**  `lastIndexOf()`'s performance degrades more noticeably with longer strings because it needs to traverse the entire string backward.
* **Use Case:** Choose `indexOf()` for finding the first occurrence and `lastIndexOf()` for the last occurrence.

Let me know if you have any other questions!

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.92 Safari/537.36

Browser/OS: Chrome 81 on Mac OS X 10.15.4

View result in a separate tab

Test name	Executions per second
lastIndexOf	30921458.0 Ops/sec
indexOf	798050816.0 Ops/sec

Related benchmarks:

index vs lastindexof empty with startIndex set to 0 (version: 0)

Comparing performance of: lastIndexOf vs indexOf

Created: 4 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 gemma2:9b, generated 27 days ago):