Benchmark: Array.isArray - MeasureThat.net

Script Preparation code:

var array = [1,3,5,7,9,20];
var value = "not an array";
var int8a = new Int8Array(6);

var isArray = Array.isArray;

function f1(v) {
  return Array.isArray(v);
}

function f2(v) {
  return isArray(v);
}

function f3(v) {
  return v instanceof Array;
}

Tests:

Array.isArray
if (!f1(array)) throw "error"; if (f1(value)) throw "error"; if (f1(int8a)) throw "error";
isArray
if (!f2(array)) throw "error"; if (f2(value)) throw "error"; if (f2(int8a)) throw "error";
instanceof
if (!f3(array)) throw "error"; if (f3(value)) throw "error"; if (f3(int8a)) throw "error";

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.isArray
isArray
instanceof

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided JSON represents a JavaScript microbenchmark test case, specifically testing the `Array.isArray` function. The benchmark is designed to measure the performance of different approaches in determining whether an object is an array.

**Options Compared**

There are three options compared:

1. **Using the built-in `Array.isArray()` method**: This approach uses the standard JavaScript function `Array.isArray()` to check if an object is an array.
2. **Creating a custom function (`f1`) using the built-in `Array.isArray()` method**: In this approach, the developer creates their own function `f1` that simply calls `Array.isArray()`.
3. **Using the instanceof operator with Array**: This approach uses the `instanceof` operator to check if an object is an instance of `Array`.

**Pros and Cons**

* **Using the built-in `Array.isArray()` method**:
	+ Pros: Fast, reliable, and widely supported.
	+ Cons: May not be available in older browsers or environments with limited JavaScript capabilities.
* **Creating a custom function (`f1`) using the built-in `Array.isArray()` method**:
	+ Pros: Allows for fine-grained control over the implementation, potentially leading to better performance.
	+ Cons: Requires additional code and may introduce overhead due to function calls.
* **Using the instanceof operator with Array**:
	+ Pros: Simple and concise, but may not be as performant as using `Array.isArray()`.
	+ Cons: May not work correctly for certain types of objects (e.g., arrays that are not instances of `Array`).

**Library and Purpose**

In this benchmark, the `Int8Array` class is used. `Int8Array` is a typed array in JavaScript that represents an array of 8-bit signed integers. Its purpose is to provide a way to work with numeric data types in JavaScript.

**Special JS Feature or Syntax**

The test case uses the `throw` statement, which is a JavaScript syntax for throwing exceptions. The `throw` statement is used to intentionally cause the benchmark to fail and measure the performance of error handling mechanisms.

**Other Considerations**

When evaluating this benchmark, it's essential to consider the following factors:

* **Browser compatibility**: The benchmark results may not be representative of all browsers or environments.
* **JavaScript version**: The benchmark may not work correctly with older JavaScript versions or specific browser implementations.
* **Optimization**: The developer may have optimized one approach over others, which could affect the fairness of the comparison.

**Alternative Approaches**

If you're interested in exploring alternative approaches to this benchmark, consider the following:

* Using other methods for determining if an object is an array, such as `typeof`, `constructor.name === "Array"`, or creating a custom function.
* Optimizing the code using techniques like inlining, caching, or memoization.
* Evaluating the performance of different JavaScript engines or browsers to compare results.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.5112.102 Safari/537.36

Browser/OS: Chrome 104 on Windows

View result in a separate tab

Test name	Executions per second
Array.isArray	1515107.5 Ops/sec
isArray	2050942.6 Ops/sec
instanceof	1501231.2 Ops/sec

Related benchmarks:

Array.isArray (version: 0)

Comparing performance of: Array.isArray vs isArray vs instanceof

Created: 4 years ago by: Guest

Jump to the latest result

Array.isArray

isArray

instanceof

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):