Benchmark: Testing lastIndexOf vs split+pop

Script Preparation code:

var str="abc:cde:def:efg:ghi";

Tests:

lastIndexOf
const lastIndexOfDot = str.lastIndexOf(':'); let snip; if (lastIndexOfDot != -1) { snip = str.substr(lastIndexOfDot + 1); } console.log(snip);
split+pop
let snip = str.split(':').pop(); console.log(snip);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lastIndexOf
split+pop

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/137.0.0.0 Safari/537.36

Browser/OS: Chrome 137 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
lastIndexOf	708085.4 Ops/sec
split+pop	701624.4 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested, compared, and some of the considerations.

**Benchmark Context**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The goal is to compare the performance of different approaches for a specific task or operation.

**Script Preparation Code**

The script preparation code is provided as `var str = "abc:cde:def:efg:ghi";;`. This creates a string variable `str` containing a colon-separated list of strings, which will be used in the benchmark tests.

**Benchmark Definition**

The benchmark definition provides two test cases:

1. **lastIndexOf**: Uses the `lastIndexOf()` method to find the last occurrence of a colon (`:`) in the `str` variable and then extracts a substring starting from the found index + 1.
2. **split+pop**: Splits the `str` string into an array using colons as delimiters, and then uses the `pop()` method to extract the last element of the array.

**Comparison**

The benchmark compares the performance of these two approaches:

* `lastIndexOf`: Uses a more traditional approach that searches for a specific character (colon) in the string and then extracts a substring.
* `split+pop`: Uses a more modern approach that splits the string into an array and then uses the `pop()` method to extract the last element.

**Pros and Cons**

**LastIndexOf Approach:**

Pros:

* Easy to understand and implement
* Suitable for finding specific characters or patterns in strings

Cons:

* Can be slower than other approaches, especially for large strings or complex patterns
* May have performance issues if the search string is very long or contains many occurrences of the target character

**Split+Pop Approach:**

Pros:

* Often faster and more efficient than traditional `lastIndexOf()` approach
* Suitable for finding the last occurrence of a specific value in an array

Cons:

* Requires splitting the string into an array, which can be slower for very large strings
* May not work as expected if the target value is not found, resulting in `undefined` or other unexpected values

**Library: None**

No JavaScript library is used in this benchmark.

**Special JS Features/Syntax: None**

There are no special JavaScript features or syntax used in this benchmark. The tests only rely on basic string operations and standard JavaScript methods.

**Alternatives**

Other alternatives for finding the last occurrence of a character or value in a string include:

* Using regular expressions with `String.prototype.lastIndexOf()` method
* Using a more modern approach like using a `Map` data structure to store indices of characters or values
* Using a library like Lodash, which provides a function called `lastIndexOf()` that can be used instead of the standard JavaScript method.

In summary, the benchmark compares two approaches for finding the last occurrence of a character in a string: traditional `lastIndexOf()` and splitting into an array using `split+pop`. The choice of approach depends on the specific requirements and performance considerations.

Related benchmarks:

Testing lastIndexOf vs split+pop (version: 0)

Comparing performance of: lastIndexOf vs split+pop

Created: 6 years ago by: Guest

Jump to the latest result

lastIndexOf

split+pop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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