Benchmark: isArray vs nullish coalesce + length check

Script Preparation code:

function myIsArray(obj){
  return (obj ?? []).length > 0;
}

var isArray = Array.isArray

Tests:

Array.isArray
isArray([])
Check object.length
myIsArray([])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.isArray
Check object.length

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 12 days ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.3.1 Safari/605.1.15

Browser/OS: Safari 18 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Array.isArray	601194432.0 Ops/sec
Check object.length	132709568.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 12 days ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON focuses on comparing two methods for determining if an object is an array: using the built-in `Array.isArray()` function and a custom function `myIsArray()` that uses the nullish coalescing operator (`??`) in combination with a length check.

### Options Compared

1. **Array.isArray()**
   - **Description**: A built-in JavaScript function specifically designed to check whether a given value is an array.
   - **Test Case**: `isArray([])`
   - **Benchmark Results**: Executions per second recorded at approximately 601 million.

2. **myIsArray()**
   - **Description**: A custom function that checks if an object is an array by returning the length of the object if it is valid; otherwise, it defaults to an empty array using the nullish coalescing operator (`??`).
   - **Test Case**: `myIsArray([])`
   - **Benchmark Results**: Executions per second recorded at approximately 132 million.

### Pros and Cons

#### Array.isArray()
- **Pros**:
  - **Performance**: The benchmark shows that `Array.isArray()` is significantly faster—nearly 4.5 times more efficient than the custom implementation.
  - **Clarity**: It clearly communicates its purpose and is widely recognized by developers, contributing to code readability and maintainability.
  - **Reliability**: The function is standard and unlikely to change across different JavaScript versions and engines, ensuring consistent behavior.

- **Cons**:
  - Compared to a simple property check, it slightly adds overhead due to its function call nature.

#### myIsArray()
- **Pros**:
  - **Flexibility**: The use of nullish coalescing allows this function to handle `null` or `undefined` inputs gracefully by returning 0 rather than throwing an error.
  - **Customizability**: Developers can modify or extend the functionality as their needs evolve.

- **Cons**:
  - **Performance**: As indicated by the benchmark results, it is considerably slower than `Array.isArray()`, meaning that in performance-critical applications, this approach might be a poor choice.
  - **Readability**: The need to understand both the nullish coalescing operator and the associated logic might make it less straightforward to a broader audience compared to the built-in method.

### Other Considerations

- The **nullish coalescing operator (`??`)** is a feature introduced in ECMAScript 2020 (ES11) that allows developers to specify a default value when dealing with `null` or `undefined`. This is particularly useful in scenarios where it is essential to differentiate between explicitly set values and the absence of a value.

### Alternatives

- **Length Check Directly**: One could argue for directly checking the `length` property on an object and validating its presence in a basic manner (e.g., `obj && obj.length > 0`), but this method lacks the clarity provided by `Array.isArray()`.
  
- **Using `instanceof`**: Another method involves using the `instanceof` operator (e.g., `obj instanceof Array`). This is generally reliable as well, but it can fail in certain scenarios (e.g., when dealing with arrays from different frames or windows).
  
- **Utility Libraries**: Many libraries like Lodash provide utility functions (e.g., `_.isArray()`) that may include additional checks or fallbacks, though they might add unnecessary overhead for simple array checks.

In conclusion, the benchmark reveals clear performance advantages for the standard `Array.isArray()` approach compared to the custom length-checking function using nullish coalescing. Software engineers should consider both performance and clarity when selecting a method for checking array types in their applications.

Related benchmarks:

isArray vs nullish coalesce + length check (version: 1)

Array.isArray vs array.length > 0

Comparing performance of: Array.isArray vs Check object.length

Created: 12 days ago by: Guest

Jump to the latest result

Array.isArray

Check object.length

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 12 days ago):