Benchmark: Array isArray vs 'in'

Script Preparation code:

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

Tests:

in
if ('field' in test) { c++; }
isArray
if (Array.isArray(test)) { c++; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
in
isArray

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Linux; Android 9; STF-L09) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.104 Mobile Safari/537.36

Browser/OS: Chrome Mobile 96 on Android

View result in a separate tab

Test name	Executions per second
in	3910191.8 Ops/sec
isArray	348179.3 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested.

**Benchmark Definition**

The benchmark measures the performance of two approaches to check if an element exists in an array: using the `in` operator and using the `Array.isArray()` method.

**Script Preparation Code**

The script preparation code creates a JavaScript array called `test` with four elements:

```javascript
var test = [1,2,3,4];
```

This is done to provide a common base for both tests. The variable `c` is declared but not used in the benchmark.

**Test Cases**

There are two test cases:

### Test Case 1: "in"

```javascript
if ('field' in test) { c++; }
```

This test uses the `in` operator to check if the string `'field'` exists as a property of the `test` array. If it does, the variable `c` is incremented.

### Test Case 2: "isArray"

```javascript
if (Array.isArray(test)) { c++; }
```

This test uses the `Array.isArray()` method to check if the `test` array is actually an array. If it is, the variable `c` is incremented.

**Library and Purpose**

In both tests, the library used is not explicitly mentioned in the provided JSON. However, based on the syntax, we can infer that the tests are using modern JavaScript features, which likely include built-in methods like `Array.isArray()`. No special libraries are required for this benchmark.

**Pros and Cons of Different Approaches**

Here's a brief analysis of each approach:

### Using `in` operator

Pros:

* Simple and concise syntax
* Works with most data structures that support property access (arrays, objects, etc.)

Cons:

* Can be slower than other methods due to the overhead of string comparison
* May not work correctly for certain types of arrays or complex data structures

### Using `Array.isArray()` method

Pros:

* Fast and efficient, as it uses a native method call
* Works with all array-like objects (not just arrays)

Cons:

* Requires an extra method call, which may incur overhead
* Less intuitive syntax compared to the `in` operator

**Other Considerations**

When choosing between these approaches, consider the following factors:

* Performance: If speed is critical, using `Array.isArray()` might be a better choice.
* Readability and maintainability: Using the `in` operator might be more readable and easier to understand for some developers.

**Alternatives**

If you want to explore other approaches or optimizations, here are some alternatives:

* Use the `hasOwnProperty()` method on objects instead of `in` to avoid returning `true` for inherited properties.
* Consider using a library like Lodash or Ramda, which provide optimized methods for array manipulation and property access.

Keep in mind that these alternatives may not be relevant for this specific benchmark, as it's focused on the basic difference between `in` and `Array.isArray()`.

Related benchmarks:

Array isArray vs 'in' (version: 0)

Comparing performance of: in vs isArray

Created: 3 years ago by: Guest

Jump to the latest result

in

isArray

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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