Benchmark: Object.defineProperty vs direct assignment

Tests:

a
let target = {}; let key = 'something'; for (let i = 0; i < 1000; i++) { Object.defineProperty(target, key + i, {value: i}); }
b
let target = {}; let key = 'something'; for (let i = 0; i < 1000; i++) { target[key + i] = i; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
a
b

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:137.0) Gecko/20100101 Firefox/137.0

Browser/OS: Firefox 137 on Linux

View result in a separate tab

Test name	Executions per second
a	12473.7 Ops/sec
b	16879.5 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

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The benchmark involves comparing two different methods of adding properties to JavaScript objects: using `Object.defineProperty` versus direct property assignment. Let's break down the test cases, their purpose, and their outcomes.

### Test Cases

1. **Test Case A: Using `Object.defineProperty`**
   - **Code**: 
     ```javascript
     let target = {};
     let key = 'something';
     
     for (let i = 0; i < 1000; i++) {
         Object.defineProperty(target, key + i, { value: i });
     }
     ```
   - **Purpose**: This approach uses the `Object.defineProperty` method to create properties on the `target` object. The method allows for more control over how properties are defined, including the ability to set property attributes such as enumerability, configurability, and writability.

2. **Test Case B: Direct Property Assignment**
   - **Code**:
     ```javascript
     let target = {};
     let key = 'something';
     
     for (let i = 0; i < 1000; i++) {
         target[key + i] = i;
     }
     ```
   - **Purpose**: This case uses straightforward direct assignment to add properties to the `target` object. It is simpler but does not provide the additional control offered by `Object.defineProperty`.

### Pros and Cons

- **Object.defineProperty**:
  - **Pros**:
    - Fine control over property attributes (e.g., setting `enumerable` to `false` to make it non-enumerable).
    - Can define getter/setter functions to create dynamic behavior for properties.
  - **Cons**:
    - Generally more performance-intensive due to the overhead of defining properties with specific attributes.
    - More verbose and potentially less readable than direct assignment for simple use cases.

- **Direct Assignment**:
  - **Pros**:
    - More straightforward and easier to read and write.
    - Tends to be faster due to less overhead, as shown in the benchmark results.
  - **Cons**:
    - Limited control over property descriptors (e.g., cannot set a property to be non-enumerable directly).

### Benchmark Results

The results show that Test Case B (direct assignment) had an executions per second rate of approximately **11331** executions, while Test Case A (using `Object.defineProperty`) had around **9395** executions. This indicates that direct assignment is noticeably faster in this benchmark.

### Considerations

1. **Use Cases**:
   - When the properties of an object need to be controlled strictly (for example, in libraries or frameworks), `Object.defineProperty` is appropriate.
   - For general object property assignments where such control is not needed, direct assignment is preferable due to its simplicity and performance benefits.

2. **Alternatives**:
   - **Using Object Spread**: In modern JavaScript (ES6 and later), the spread operator (`{ ...object }`) provides a way to create shallow copies of objects and merge properties more elegantly.
   - **Object.assign**: This is another method for copying properties from one or more source objects to a target object.

In summary, the benchmark is testing the performance of two approaches for setting object properties in JavaScript, with the insights revealing that direct assignment is faster and simpler than using `Object.defineProperty` in the tested scenarios. Choosing between these options depends primarily on whether you need the additional features offered by `Object.defineProperty`.

Related benchmarks:

Object.defineProperty vs direct assignment (version: 1)

Comparing performance of: a vs b

Created: one year ago by: Guest

Jump to the latest result

a

b

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):