Benchmark: JavaScript object spread operator lead & tail

Tests:

Lead
const mockObject = { a: 'qwerty', b: 'bob', c: 'Lorem', d: 'Ipsum', e: 'dummy', f: 'text' } const finalObject = { g: 'Test', ...mockObject, };
Tail
const mockObject = { a: 'qwerty', b: 'bob', c: 'Lorem', d: 'Ipsum', e: 'dummy', f: 'text' } const finalObject = { ...mockObject, g: 'Test', };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Lead
Tail

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Browser/OS: Chrome 132 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Lead	11763098.0 Ops/sec
Tail	49361584.0 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 provided benchmark definition and test cases.

**Benchmark Definition**

The JSON data represents a JavaScript microbenchmark that tests the performance of the object spread operator (`...`) in two different scenarios: "Lead" and "Tail".

**Options Compared**

In this benchmark, we have two main options being compared:

1. **Leading Spread**: In the "Lead" test case, the spread operator is used as the first operand, i.e., `const finalObject = { ...mockObject, g: 'Test' }`. This means that the properties of `g` are spread before those of `mockObject`.
2. **Trailing Spread**: In the "Tail" test case, the spread operator is used as the second operand, i.e., `const finalObject = { ...mockObject, g: 'Test' }`. This means that the properties of `g` are appended after those of `mockObject`.

**Pros and Cons**

- **Leading Spread**: 
    - Pros:
        * Can be faster for larger objects, as it avoids creating intermediate arrays.
        - Can be more readable when working with large datasets.
    - Cons:
        * May incur higher memory overhead due to the creation of intermediate arrays.

- **Trailing Spread**:
    - Pros:
        * Avoids the potential memory overhead of intermediate arrays.
        - Can be beneficial for smaller objects or when working with nested properties.
    - Cons:
        * May incur slower performance on large datasets, as it requires concatenation and array creation.

**Library**

In both test cases, no external library is explicitly mentioned. However, the use of the spread operator (`...`) suggests that JavaScript's built-in object features are being utilized.

**Special JS Feature or Syntax**

The use of the spread operator (`...`) in this benchmark highlights a relatively recent addition to the ECMAScript standard (ES6) for creating new objects by copying properties from an existing object. This syntax is a concise way to merge two objects, with the second operand's properties being appended to the first.

**Alternative Approaches**

In the absence of the spread operator or if it were not available, alternative approaches might have been used:

- For leading spreads:
    - Using `Object.assign()` method to concatenate the object literals.
    - Creating intermediate arrays and then concatenating them.
- For trailing spreads:
    - Manual concatenation using string interpolation or array methods.

However, these alternatives would likely incur higher overhead in terms of performance and memory usage compared to the spread operator approach.

Related benchmarks:

JavaScript object spread operator lead & tail (version: 1)

Comparing performance of: Lead vs Tail

Created: one year ago by: Registered User

Jump to the latest result

Lead

Tail

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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