Benchmark: Object rename: reduce vs fromEntries vs assign & delete

Script Preparation code:

obj = { "a": 1, "b": 'string', c: {hi:'ho'} };
prefix = "_";

Tests:

reduce
return Object.keys(obj).reduce(function (result, key) { result[prefix + key] = obj[key]; return result; }, {});
fromEntries
return Object.fromEntries( Object.entries(obj).map(([k, v]) => [`${prefix}${k}`, v]) )
assign & delete
for (const key in obj) { obj[prefix+key] = obj[key]; delete obj[key]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce
fromEntries
assign & delete

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/145.0.0.0 Safari/537.36

Browser/OS: Chrome 145 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
reduce	8471822.0 Ops/sec
fromEntries	4437298.5 Ops/sec
assign & delete	10286.1 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark test case, specifically designed to compare the performance of three different approaches for renaming object properties.

**Benchmark Definition**

The benchmark is defined by a single script that creates an object `obj` with several properties: `"a": 1`, `"b"` (a string), and a nested object `c` with a property `hi`. The script also defines a prefix `_`.

**Test Cases**

There are three test cases, each representing one of the approaches:

1. **"reduce"`:
This approach uses the `Array.prototype.reduce()` method to rename the properties. It iterates over the object's keys, creating a new key-value pair for each property, and returns an empty object.
2. **"fromEntries"`:
This approach uses the `Object.fromEntries()` method to create a new object from an array of key-value pairs. The `Object.entries()` method is used to get an array of the object's key-value pairs, which are then mapped to include the prefix in each key.
3. **"assign & delete"`:
This approach uses a simple loop to rename the properties by assigning the original value to the new key and then deleting the original key.

**Pros and Cons**

1. **"reduce"`:
	* Pros: efficient use of `Array.prototype.reduce()` method, which is optimized for performance.
	* Cons: may not be as readable or maintainable due to its concise nature.
2. **"fromEntries"`:
	* Pros: more readable and maintainable than the other two approaches, uses modern methods that are widely adopted.
	* Cons: may have slightly higher overhead due to the creation of an array and object.
3. **"assign & delete"`:
	* Pros: simple and easy to understand, avoids potential pitfalls with `fromEntries`.
	* Cons: may be slower than the other two approaches due to the repeated assignments and deletions.

**Library and Features**

No libraries are used in this benchmark. However, some features of JavaScript are implicitly used:

1. **`Array.prototype.reduce()`**: a built-in method for reducing an array to a single value.
2. **`Object.entries()`**: a built-in method for getting an array of key-value pairs from an object.
3. **`Object.fromEntries()`**: a built-in method for creating an object from an array of key-value pairs (available in ECMAScript 2020+).

**Alternatives**

If you're looking for alternative approaches, consider the following:

1. Using `Object.assign()` to create a new object with renamed properties.
2. Using a library like Lodash (`_`) to rename object properties, which can provide more flexibility and readability.

Note that these alternatives may have different performance characteristics compared to the original three approaches.

Related benchmarks:

Object rename: reduce vs fromEntries vs assign & delete (version: 0)

Comparing performance of: reduce vs fromEntries vs assign & delete

Created: 4 years ago by: Guest

Jump to the latest result

reduce

fromEntries

assign & delete

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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