Benchmark: 39ut983u4t983h93uz

Script Preparation code:

var test = [1,2,3,4];
var c;

Tests:

Instanceof
if (test instanceof Array) { c++; }
isArray
if (Array.isArray(test)) { c++; }
prototype.toString
if (Object.prototype.toString.call(test).slice(8, -1) === 'Array') { c++; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Instanceof
isArray
prototype.toString

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON files and explain what is tested, compared, and considered in each approach.

**Benchmark Definition**

The first JSON file represents a benchmark definition, which includes:

* `Name`: A unique identifier for the benchmark.
* `Description`: An optional description of the benchmark (empty in this case).
* `Script Preparation Code`: The JavaScript code that prepares the test data. In this case, it simply declares an array variable `test` and assigns it a value `[1,2,3,4]`.
* `Html Preparation Code`: An optional section for HTML preparation code (empty in this case).

**Individual Test Cases**

The second JSON file represents individual test cases, each with:

* `Benchmark Definition`: A JavaScript statement that tests the specified condition on the prepared test data.
* `Test Name`: The name of the test.

Let's analyze each test case:

1. **`Instanceof`**: This test checks if the `test` variable is an instance of a specific type using the `instanceof` operator. In this case, it will return `true` because `test` is an array.
2. **`isArray`**: This test uses the `Array.isArray()` function to check if `test` is an array. This method is similar to `instanceof`, but it returns a boolean value (`true` or `false`) instead of using the `instanceof` operator.
3. **`prototype.toString`**: This test checks if `Object.prototype.toString.call(test)` returns a string that starts with `'Array'`. This method uses the `toString()` method on the prototype of the `test` object, which is an array in this case.

**Comparison and Considerations**

The three tests compare different ways to check if a variable is an array. Here are some pros and cons of each approach:

* **`instanceof`**: Pros:
	+ Simple and straightforward.
	+ Works well for most cases.
Cons:
	+ Can be slower due to the virtual function call.
	+ May not work correctly with some legacy browsers or environments.
* **`Array.isArray()`**: Pros:
	+ Faster than `instanceof`.
	+ More explicit and readable.
Cons:
	+ Not supported in older versions of Internet Explorer (IE).
	+ May not work correctly if the variable is a function or an object that has an array-like property.
* **`prototype.toString`**: Pros:
	+ Works even in older browsers that don't support `Array.isArray()`.
Cons:
	+ Less explicit and less readable than the other two methods.
	+ May require more code to handle edge cases (e.g., null or undefined values).

**Library: `Object.prototype.toString.call()`**

The `Object.prototype.toString.call(test)` method is a part of the JavaScript language specification. It calls the `toString()` method on the prototype object of the given argument (`test`) and returns its result as a string. In this case, it's used to check if an object is an array by verifying that its `toString()` representation starts with `'Array'`.

**Special JS Features or Syntax**

The provided benchmark doesn't include any special JavaScript features or syntax, such as ES6 classes, async/await, or modern modules. The tests focus on basic array checks using the methods mentioned above.

**Other Alternatives**

Some alternative approaches to check if a variable is an array include:

* Using a regular expression (`test instanceof RegExp.test ? test : null`)
* Creating a custom function `isArray(test) { return Array.isArray(test); }`
* Using a library like Lodash's `isArray()` function

However, these alternatives might not be as efficient or readable as the original tests.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36 Edg/112.0.1722.58

Browser/OS: Chrome 112 on Windows

View result in a separate tab

Test name	Executions per second
Instanceof	6872506.0 Ops/sec
isArray	6879878.0 Ops/sec
prototype.toString	6107540.5 Ops/sec

Related benchmarks:

39ut983u4t983h93uz (version: 0)

Comparing performance of: Instanceof vs isArray vs prototype.toString

Created: one year ago by: Guest

Jump to the latest result

Instanceof

isArray

prototype.toString

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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