Benchmark: Compare lastindexOf + substr vs split + slice

Tests:

1
var s = 'sdfsdfsdf.asdasdasdasdasd.1231231'; console.log(s.substr(s.lastIndexOf('.') + 1));
2
var s = 'sdfsdfsdf.asdasdasdasdasd.1231231'; console.log(s.split('.').slice(-1));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
1
2

Fastest: N/A

Slowest: N/A

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

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Let's dive into the world of MeasureThat.net and explore what's being tested in this benchmark.

**What is being tested?**

The provided JSON represents two test cases that compare the performance of two approaches to extract a substring from a string:

1. `substr(s, lastIndex) + ...` (Test Case 1)
2. `split('.', ...).slice(-1)` (Test Case 2)

In both cases, we're trying to retrieve the last part of a string after a specified separator (`.`).

**Options compared:**

The two approaches being tested are:

A. Using `substr(s, lastIndex)`, which extracts a substring starting from the index of the last occurrence of the separator.

B. Using `split('.', ...).slice(-1)`, which splits the string into parts using the separator and then takes the last part.

**Pros and Cons:**

1. **Approach A (substr)**:
	* Pros:
		+ Efficient for large strings, as it only requires a single pass to find the last index.
		+ Fast in terms of code execution time.
	* Cons:
		+ May not work correctly if `lastIndex` is negative or undefined.
		+ Can be slower than other methods if the string contains many consecutive separators.
2. **Approach B (split + slice)**:
	* Pros:
		+ Robust and reliable, as it doesn't rely on a single index calculation.
		+ Works correctly even when `lastIndex` is negative or undefined.
	* Cons:
		+ May be slower due to the overhead of creating an array from splitting the string.

**Library usage:**

There is no explicit library mentioned in this benchmark. However, some JavaScript engines might optimize certain methods like `substr()` or `slice()` internally using built-in functions or techniques, which could affect performance.

**Special JS feature/syntax:**

This benchmark doesn't appear to use any special JavaScript features or syntax beyond standard language support.

**Other alternatives:**

In addition to the two approaches tested, other possible methods for extracting a substring from a string include:

* Using `replace()` with a regular expression to find and extract the last part of the string.
* Implementing a custom search algorithm using techniques like binary searching or interpolation.
* Utilizing specialized libraries like `lodash` or `underscore`, which provide utility functions for string manipulation.

It's worth noting that MeasureThat.net is designed to test JavaScript engine-specific optimizations, so benchmark results may not be directly comparable across different engines or environments.

Related benchmarks:

Compare lastindexOf + substr vs split + slice (version: 0)

new

Comparing performance of: 1 vs 2

Created: 6 years ago by: Guest

Jump to the latest result

1

2

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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