Benchmark: undefined vs evaluation vs hasOwnProperty

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };

Tests:

undefined
obj['d'] !== undefined;
evaluation
obj['d'];
hasOwnProperty
obj.hasOwnProperty( 'd' );

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
evaluation
hasOwnProperty

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:133.0) Gecko/20100101 Firefox/133.0

Browser/OS: Firefox 133 on Windows

View result in a separate tab

hasOwnProperty

529.4M/s

evaluation

492.6M/s

undefined

447.9M/s

View exact numbers

Test name	Executions per second
✓ hasOwnProperty	529,391,520 Ops/sec
evaluation	492,647,136 Ops/sec
undefined	447,941,024 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark is designed to measure the performance of object lookup in JavaScript. Specifically, it compares three approaches:

1. **Direct Access (`obj['d'] !== undefined;`)**: This approach directly accesses the property `d` on the object `obj`.
2. **Evaluation (`obj['d'];`)**: This approach evaluates the expression `obj['d']`, which returns the value of the property `d`.
3. **hasOwnProperty (`obj.hasOwnProperty('d');`)**: This approach uses the `hasOwnProperty` method to check if the object has a property named `d`.

**Options Comparison**

The three approaches have different pros and cons:

*   **Direct Access**: Pros:
    *   Fastest, as it directly accesses the property without any additional checks or evaluations.
    *   Most straightforward approach.
*   Cons:
    *   Will throw an error if the property does not exist on the object (i.e., `obj['d'] !== undefined;` would return `true`, but accessing `obj['d']` would throw an exception).
*   **Evaluation (`obj['d'];`)**: Pros:
    *   Safe, as it will return `undefined` if the property does not exist.
*   Cons:
    *   Generally slower than direct access due to the additional evaluation step.
*   **hasOwnProperty (`obj.hasOwnProperty('d');`)**: Pros:
    *   Safe, similar to the evaluation approach, returning `false` if the property does not exist.
*   Cons:
    *   Slower than direct access due to the additional method call.

**Library and Special JS Features**

None of the benchmark cases explicitly uses any libraries or special JavaScript features. The tests rely solely on built-in JavaScript functionality.

However, it's worth noting that the `hasOwnProperty` method is a part of the ECMAScript standard, which means its behavior is consistent across different browsers and environments.

**Other Alternatives**

Some alternative approaches to object lookup could include:

*   **Using the in operator (`in obj; obj['d'];`)**: This approach checks if the property exists using the `in` operator and then accesses it. While this can be a safe approach, it's generally slower than direct access or evaluation due to the additional steps.
*   **Using bracket notation with optional chaining (`obj?.['d'] ?? undefined;`)**: This is a more modern approach that uses optional chaining (introduced in ECMAScript 2020) to safely navigate the object. While this approach can be safer than direct access, it's not as straightforward and may have performance implications depending on the specific use case.

These alternatives are not included in the original benchmark but demonstrate other ways to approach object lookup in JavaScript.

undefined vs evaluation vs hasOwnProperty (version: 0) Benchmark.js

Object lookup performance

Comparing performance of: `undefined vs evaluation vs hasOwnProperty`

Created: 3 years ago by: Guest

Go to the latest result

undefined

evaluation

hasOwnProperty

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

undefined vs evaluation vs hasOwnProperty (version: 0) Benchmark.js

Object lookup performance

Comparing performance of: undefined vs evaluation vs hasOwnProperty

Created: 3 years ago by: Guest

Go to the latest result

undefined

evaluation

hasOwnProperty

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `undefined vs evaluation vs hasOwnProperty`