Benchmark: Object.assign vs. JavaScript Polyfill Example

Script Preparation code:

const sourceObjects = [];
const destObjects = [];

for (let i = 0; i < 500; ++i) {
    const sourceObject = {};
    for (let j = 0; j < 10; ++j) {
        sourceObject[Math.random().toFixed(0) * 1000] = Math.random().toFixed(0) * 1000;
    }
  
    const destObject = {};
    for (let j = 0; j < 5; ++j) {
        destObject[Math.random().toFixed(0) * 1000] = Math.random().toFixed(0) * 1000;
    }
  
    sourceObjects.push(sourceObject);
    destObjects.push(destObject);
}

window.sourceObjects = sourceObjects;
window.destObjects = destObjects;

Tests:

Object.assign
const sourceObjects = window.sourceObjects; const destObjects = window.destObjects; for (let i = 0; i < sourceObjects.length; ++i) { const destObject = destObjects[i]; const sourceObject = sourceObjects[i]; const newObject = Object.assign(destObject, sourceObject); }
Polyfill Extend
function objForEachKey(target, callbackfn) { if (target) { for (var prop in target) { if (Object.prototype.hasOwnProperty.call(target, prop)) { callbackfn.call(target, prop, target[prop]); } } } } function extend(obj, obj2, obj3, obj4, obj5) { // Variables var extended = {}; var deep = false; var i = 0; var length = arguments.length; var objProto = Object.prototype; var theArgs = arguments; // Check if a deep merge if (objProto.toString.call(theArgs[0]) === "[object Boolean]") { deep = theArgs[0]; i++; } // Loop through each object and conduct a merge for (; i < length; i++) { var obj = theArgs[i]; objForEachKey(obj, function (prop, value) { extended[prop] = value; }); } return extended; } const sourceObjects = window.sourceObjects; const destObjects = window.destObjects; for (let i = 0; i < sourceObjects.length; ++i) { const destObject = destObjects[i]; const sourceObject = sourceObjects[i]; const newObject = extend(destObject, sourceObject); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.assign
Polyfill Extend

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**What is tested?**

The benchmark compares two approaches to merge objects in JavaScript:

1. `Object.assign()`: A built-in method that copies properties from one or more source objects to a target object.
2. A custom implementation, known as "Polyfill Extend", which achieves the same result using a loop and recursion.

**Options compared:**

* The benchmark compares the performance of `Object.assign()` vs. the Polyfill Extend implementation.
* Both approaches aim to merge two arrays of objects into one array with merged objects.

**Pros and Cons:**

* **Object.assign()**:
	+ Pros: Efficient, widely supported, and easy to use.
	+ Cons: May not work as expected if the source or target object is not an object, and it only copies enumerable properties.
* **Polyfill Extend**:
	+ Pros: Customizable, can handle non-enumerable properties, and can be used with any type of data structure.
	+ Cons: More complex to implement, may have performance overhead due to the recursive loop.

**Library/Extension:**

In this benchmark, there is no explicit library or extension being tested. However, the Polyfill Extend implementation uses a custom `objForEachKey()` function and an `extend()` function from the Lodash library (not explicitly mentioned in the benchmark code). The use of Lodash suggests that the test author wanted to compare the performance of `Object.assign()` against a well-known polyfill implementation.

**Special JS feature or syntax:**

There are no special JavaScript features or syntax being tested in this benchmark. Both approaches rely on standard JavaScript constructs.

**Other alternatives:**

If you're interested in exploring alternative merge methods, here are a few:

* **Lodash's `_.merge()`**: A built-in method that merges two objects into one.
* **ES6's `Object.assign()` with spread syntax**: An updated implementation of `Object.assign()` using the spread operator (`{ ... }`).
* **Manual loop-based merge**: Implementing a custom merge function from scratch, similar to the Polyfill Extend approach.

In conclusion, this benchmark provides a useful comparison between two approaches to merging objects in JavaScript. By choosing one or both of these methods, developers can optimize their code for performance and readability.

Related benchmarks:

Object.assign vs. JavaScript Polyfill Example (version: 1)

Comparing Object.assign vs. a JavaScript Implementation that achieves the same thing

Comparing performance of: Object.assign vs Polyfill Extend

Created: 4 years ago by: Registered User

Jump to the latest result

Object.assign

Polyfill Extend

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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