Benchmark: Object assign vs polyfill

Script Preparation code:

var a = {a:1, b:2, c:3};

function ownKeys(object, enumerableOnly) { var keys = Object.keys(object); if (Object.getOwnPropertySymbols) { var symbols = Object.getOwnPropertySymbols(object); if (enumerableOnly) symbols = symbols.filter(function (sym) { return Object.getOwnPropertyDescriptor(object, sym).enumerable; }); keys.push.apply(keys, symbols); } return keys; }

function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; if (i % 2) { ownKeys(source, true).forEach(function (key) { _defineProperty(target, key, source[key]); }); } else if (Object.getOwnPropertyDescriptors) { Object.defineProperties(target, Object.getOwnPropertyDescriptors(source)); } else { ownKeys(source).forEach(function (key) { Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key)); }); } } return target; }

function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }

Tests:

Polyfill
var b = _objectSpread({}, a, { d: 4 });
Object assign
var b = Object.assign({}, a, { d: 4 });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Polyfill
Object assign

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its options.

**Benchmark Definition:**

The benchmark definition provides two different approaches to merge objects in JavaScript:

1. **Object.assign():**

`var b = Object.assign({}, a, { d: 4 });`

This approach uses the built-in `Object.assign()` method to merge the properties of two or more objects into one.

2. **Polyfill (ownKeys and _objectSpread functions):**

```javascript
function ownKeys(object, enumerableOnly) {
    var keys = Object.keys(object);
    if (Object.getOwnPropertySymbols) {
        var symbols = Object.getOwnPropertySymbols(object);
        if (enumerableOnly) symbols = symbols.filter(function (sym) { return Object.getOwnPropertyDescriptor(object, sym).enumerable; });
        keys.push.apply(keys, symbols);
    }
    return keys;
}

These functions are used to create a polyfill for the `Object.assign()` method that works in older browsers where it was not supported.

**Options Compared:**

The two options compared in this benchmark are:

1.  Using the built-in `Object.assign()` method.
2.  Using custom functions (`ownKeys` and `_objectSpread`) to create a polyfill for `Object.assign()`.

**Pros and Cons:**

*   **Using `Object.assign()`:**
    *   Pros:
        *   Faster execution, as it leverages the built-in optimization of the browser.
        *   Less code to write and maintain.
    *   Cons:
        *   May not work in older browsers that do not support `Object.assign()`.
*   **Using custom polyfill functions (`ownKeys` and `_objectSpread`):**
    *   Pros:
        *   Works in all browsers, including older ones where `Object.assign()` is not supported.
        *   Can be customized to fit specific use cases or performance requirements.
    *   Cons:
        *   Slower execution, as it involves additional function calls and logic.
        *   More code to write and maintain.

**Other Considerations:**

*   The choice between using `Object.assign()` and a custom polyfill depends on the target audience of your application. If you need support for older browsers, the polyfill is necessary. Otherwise, using `Object.assign()` is likely faster and more efficient.
*   When creating a custom polyfill, consider optimizing the functions to minimize overhead and maximize performance.

**Alternative Approaches:**

Other approaches to merge objects include:

1.  **Using the spread operator (`{ ... }`):**
    *   Example: `var b = { ...a, d: 4 };`
2.  **Using the `merge` function from a library like Lodash:**
    *   Example: `var b = _.merge({}, a, { d: 4 });`

These alternatives may have their own pros and cons, depending on the specific use case and requirements of your application.

Keep in mind that the performance differences between these approaches can be subtle, and other factors like caching, optimization, or parallel execution might affect the actual performance difference.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Windows

View result in a separate tab

Test name	Executions per second
Polyfill	208591.8 Ops/sec
Object assign	2116492.8 Ops/sec

Related benchmarks:

Object assign vs polyfill (version: 0)

Comparing performance of: Polyfill vs Object assign

Created: 5 years ago by: Guest

Jump to the latest result

Polyfill

Object assign

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):