Benchmark: Array checking: isArray vs val.with

Script Preparation code:

var array = [1,2,3,4];
var string = '[1,2,3,4]';
var c;

Tests:

Prop check on array
if (array.with) { c++; } else { c++; }
isArray on array
if (Array.isArray(array)) { c++; } else { c++; }
Prop check on string
if (string.with) { c++; } else { c++; }
isArray on string
if (Array.isArray(string)) { c++; } else { c++; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Prop check on array
isArray on array
Prop check on string
isArray on string

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Prop check on array	5033140.5 Ops/sec
isArray on array	4827220.5 Ops/sec
Prop check on string	4943017.5 Ops/sec
isArray on string	4884689.5 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 days ago):

LLMs can make mistakes. Check important info.

The provided benchmark is focused on comparing two approaches for checking if a value is an array in JavaScript. The benchmark tests both the use of the built-in `Array.isArray()` method and a property check on the values.

### Description of Test Cases

1. **Prop check on array**: 
   - **Code**: `if (array.with) { c++; } else { c++; }`
   - **Test Name**: "Prop check on array"
   - **Purpose**: This test attempts to check if the `with` property exists on the `array` object. Since arrays are JavaScript objects and can have properties, this is essentially checking for a property that does not exist on arrays.
  
2. **isArray on array**: 
   - **Code**: `if (Array.isArray(array)) { c++; } else { c++; }`
   - **Test Name**: "isArray on array"
   - **Purpose**: This checks if the `array` variable is indeed an array, using the built-in `Array.isArray()` method, which is the standard approach in JavaScript for determining if a given variable is an array.

3. **Prop check on string**: 
   - **Code**: `if (string.with) { c++; } else { c++; }`
   - **Test Name**: "Prop check on string"
   - **Purpose**: Similar to the previous `Prop check`, this test evaluates the `string` variable to see if it contains a property named `with`, which it does not, similar to the check performed on the array.

4. **isArray on string**: 
   - **Code**: `if (Array.isArray(string)) { c++; } else { c++; }`
   - **Test Name**: "isArray on string"
   - **Purpose**: This checks if the `string` variable is an array, using `Array.isArray()`, which confirms that strings are not arrays.

### Pros and Cons of Approaches

#### 1. Property Check
   - **Pros**:
     - Can be fast for checking properties directly due to its simplicity.
     - Potentially suitable in environments or scenarios where custom properties have been added.
   - **Cons**:
     - Not a reliable method for type checking, as it does not actually validate whether the variable is an array.
     - This approach may return false positives if a property exists by any means (including inheritance).
     - Parsing through the prototype chain can lead to false results if properties are overridden or shadowed.

#### 2. `Array.isArray()`
   - **Pros**:
     - Provides a reliable way to determine if a variable is an array, as it strictly checks for the type.
     - Built-in method, optimized and maintained for performance in most JavaScript engines.
   - **Cons**:
     - Slightly more computationally intensive compared to a direct property check, but this is generally negligible in modern applications where reliability is paramount.

### Results Overview
Based on the latest benchmark results:

- **Prop Check on Array**: 5,033,140.5 executions per second
- **Prop Check on String**: 4,943,017.5 executions per second
- **isArray on Array**: 4,827,220.5 executions per second
- **isArray on String**: 4,884,689.5 executions per second

Despite the higher performance of the property checks, the reliability and correctness of `Array.isArray()` make it the preferred method for determining if a variable is an array in practical applications.

### Other Considerations
When choosing between these methods, developers must keep in mind the context in which array-type checking is necessary. For a large-scale production environment where maintaining code reliability and correctness is critical, it is advisable to use `Array.isArray()`. Property checks may be leveraged in performance-critical sections of code but come with inherent risks concerning accuracy.

### Alternatives
Other alternatives for checking the type of a variable in JavaScript include:

- Using `instanceof Array`: 
  - Example: `array instanceof Array`
  - Pros: Gives a true/false depending on prototype chain
  - Cons: Can return false for arrays created in different execution contexts (e.g., iframes).

- Using the `Object.prototype.toString.call(value)`: 
  - Example: `Object.prototype.toString.call(value) === '[object Array]'`
  - Pros: Highly reliable across different execution contexts.
  - Cons: Slightly more verbose than the other methods.

In conclusion, while the benchmark showcases raw execution speed for different approaches, it is essential to consider accuracy, context, and the long-term maintainability of the code.

Related benchmarks:

Array checking: isArray vs val.with (version: 1)

Comparing performance of: Prop check on array vs isArray on array vs Prop check on string vs isArray on string

Created: 2 days ago by: Guest

Jump to the latest result

Prop check on array

isArray on array

Prop check on string

isArray on string

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 days ago):