Benchmark: array[0] vs array.length > 0

Script Preparation code:

var arr = [];

Tests:

array length
if (arr[0]) { console.log(1); } else { console.log(0); }
array length > 0
if (arr.length > 0) { console.log(1); } else { console.log(0); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array length
array length > 0

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 23 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
array length	727955.8 Ops/sec
array length > 0	721651.8 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 26 days ago):

LLMs can make mistakes. Check important info.

The benchmark represented in this JSON compares two different approaches to checking whether an array is empty in JavaScript. Specifically, it tests the performance of:

1. **Accessing the first element of the array**: `if (arr[0]) {...}`
2. **Checking the length of the array**: `if (arr.length > 0) {...}`

### Explanation of Test Cases

#### 1. `if (arr[0]) {...}`
- **Test Name**: "array length "
- **Benchmark Definition**: This conditional checks the truthy value of the first element of the array (`arr[0]`). If `arr[0]` exists and is truthy (meaning it’s not `undefined`, `null`, `0`, or an empty string), it logs `1`, otherwise it logs `0`.

#### 2. `if (arr.length > 0) {...}`
- **Test Name**: "array length > 0 "
- **Benchmark Definition**: This conditional checks if the number of elements in the array is greater than zero by evaluating the `length` property of the array. If the length is greater than zero, it logs `1`, otherwise it logs `0`.

### Comparison of the Approaches

#### Pros and Cons

1. **Using `arr[0]`**:
   - **Pros**:
     - This approach can be slightly faster in cases where the array is large and checking the first element provides immediate feedback about whether the array is empty without needing to count all elements.
     - It's straightforward for arrays expected to contain non-falsy values.
   - **Cons**:
     - It fails for empty arrays and arrays that start with a falsy first element (like `0`, `false`, or `''`). Therefore, it may lead to incorrect conclusions about whether the array has elements if the first element is unreliable.
   
2. **Using `arr.length > 0`**:
   - **Pros**:
     - This method is reliable regardless of the contents of the array. It directly checks the number of elements, making it a more fail-safe option for determining if an array is empty.
   - **Cons**:
     - This approach may involve an additional property access and comparison, which could be marginally slower in some scenarios, especially if the JavaScript engine optimizations favor one approach over the other.

### Performance Results

From the benchmark results:
- Execution speed for the first test (`if (arr[0]) {...}`) was approximately **547093.44 executions per second**.
- Execution speed for the second test (`if (arr.length > 0) {...}`) was approximately **546467.56 executions per second**.

While both methods show similar performance, the first method (`arr[0]`) performed marginally faster in this test.

### Additional Considerations

- **Use Cases**: The choice of method may depend on the context in which it is used. If you are sure that the array will always contain valid values that are non-falsy and that the first element can be trusted for checks, the first method might be suitable. If the array may contain falsy values or if it’s critical that no empty checks are mishandled, the second method (`arr.length > 0`) is recommended.
  
- **Code Readability**: In terms of readability, `arr.length > 0` clearly communicates the intent of checking for emptiness, which can be beneficial for maintainability.

### Alternatives

Other alternatives to check if an array is empty might include:
- **Using a combination of both**: Checking if array length is zero could also involve checking `!arr.length`.
- **Using helper functions or libraries**: Libraries like Lodash offer utilities such as `_.isEmpty()`, which can check for an empty array or object and enhance code clarity.
- **Strict Equality Check**: Making explicit checks using `===` to avoid any unwanted coercion in specific contexts.

In summary, both methods have their place in JavaScript performance benchmarks, and the choice may ultimately depend on specific application requirements and developer preference.

Related benchmarks:

array[0] vs array.length > 0 (version: 1)

Comparing performance of: array length vs array length > 0

Created: 27 days ago by: Guest

Jump to the latest result

array length

array length > 0

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 26 days ago):