Benchmark: slice vs substr (negative index)

Script Preparation code:

var example = 'the cake is a lie'

Tests:

slice
var result = example.slice(-5)
substr
var result = example.substr(-5)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
substr

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the benchmark definition and test cases to understand what is being tested.

**Benchmark Definition:**
The benchmark compares the performance of two JavaScript methods, `slice()` and `substr()`, when used with a negative index. The benchmark aims to identify which method is faster and more efficient in this specific scenario.

**Script Preparation Code:**
The script preparation code defines a variable `example` as a string literal, containing the phrase "the cake is a lie".

**Html Preparation Code:**
There is no HTML preparation code provided, suggesting that this is a simple JavaScript-only benchmark.

**Individual Test Cases:**

1. **slice()**: The first test case measures the performance of using `slice()` with a negative index (`example.slice(-5)`). This will attempt to extract 5 characters from the end of the string.
2. **substr()**: The second test case measures the performance of using `substr()` with a negative index (`example.substr(-5)`).

**Library Usage:**
None of the test cases explicitly use any external libraries.

**Special JS Feature/Syntax:**
The benchmark takes advantage of JavaScript's array-like object behavior, where indexing with a negative number will start from the end of the string. This is an inherent feature of JavaScript and not specific to any library or syntax.

**Pros and Cons of Different Approaches:**

* **slice()**: When used with a negative index, `slice()` attempts to extract characters from the end of the array-like object (in this case, the string). This approach can be faster when dealing with large strings because it avoids creating a new intermediate result.
	+ Pros: efficient when extracting characters from the end
	+ Cons: may not work as expected for non-string inputs or when used with very large arrays
* **substr()**: When used with a negative index, `substr()` also attempts to extract characters from the end of the array-like object. However, it creates an intermediate result and returns it, which can be slower than `slice()`.
	+ Pros: easy to use and readable
	+ Cons: may create unnecessary intermediate results

**Other Alternatives:**
In modern JavaScript, you could also use other methods like `substring()` or `String.prototype.slice()` with a negative index. However, these methods are essentially the same as `slice()` and `substr()`, respectively.

**Benchmark Results:**
The latest benchmark result shows that Chrome 115 executed the `slice()` test case 1,463,248 more times per second than the `substr()` test case on a Mac OS X 10.15.7 machine with a Desktop platform. This suggests that `slice()` is faster and more efficient in this specific scenario.

Keep in mind that benchmark results may vary depending on the JavaScript engine, system resources, and other factors. These results should be taken as a general indication of performance differences between `slice()` and `substr()` when used with negative indices.

Related benchmarks:

slice vs substr (negative index) (version: 0)

Compares slice and substr against each other when there is a negative index provided

Comparing performance of: slice vs substr

Created: 2 years ago by: Guest

Jump to the latest result

slice

substr

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):