Benchmark: Convert Array to Object - Compare all possible4

Script Preparation code:

var data = Array.from(Array(10000).keys()).map(i => ({id: i, value: `val_${i}`}));

Tests:

Object.fromEntries
Object.fromEntries(data.map(obj => [obj.id, obj]));
Reduce (reuse object)
data.reduce((acc, obj) => { acc[obj.id] = obj; return acc; }, {});
Reduce (creating temporary objects)
data.reduce((acc, obj) => ({ ...acc, [obj.id]: obj }), {});
Map
new Map(data.map(obj => [obj.id, obj]));
forEach
const res = {}; data.forEach(obj => { res[obj.id] = obj; });
for of
const res = {}; for (const obj of data) { res[obj.id] = obj; }
for i
const res = {}; for (let i = 0; i < data.length; i++) { const obj = data[i]; res[obj.id] = obj; }
for i saved length variable
const res = {}; const length = data.length; for (let i = 0; i < length; i++) { const obj = data[i]; res[obj.id] = obj; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.fromEntries
Reduce (reuse object)
Reduce (creating temporary objects)
Map
forEach
for of
for i
for i saved length variable

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Object.fromEntries	2715.7 Ops/sec
Reduce (reuse object)	18107.6 Ops/sec
Reduce (creating temporary objects)	121.1 Ops/sec
Map	2077.8 Ops/sec
forEach	18834.5 Ops/sec
for of	18485.0 Ops/sec
for i	1461.3 Ops/sec
for i saved length variable	2625.2 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The provided benchmark measures the performance of different approaches for converting an array to an object.

**Benchmark Definition**

The benchmark definition consists of a JSON object with several properties:

* `Name`: The name of the benchmark, which is "Convert Array to Object - Compare all possible".
* `Description`: An empty string indicating that there is no description provided.
* `Script Preparation Code`: A JavaScript code snippet that prepares an array of 10,000 objects, each with an `id` and a `value`.
* `Html Preparation Code`: An empty string indicating that no HTML preparation code is required.

**Individual Test Cases**

The benchmark consists of six individual test cases, each representing a different approach for converting the array to an object:

1. **Object.fromEntries**: Uses the `Object.fromEntries` method to create an object from an array of key-value pairs.
2. **Reduce (reuse object)**: Uses the `reduce` method with an accumulator object and pushes new properties onto it, overwriting existing ones.
3. **Reduce (creating temporary objects)**: Similar to the previous approach, but creates a new object for each iteration instead of reusing an accumulator object.
4. **Map**: Uses the `Map` constructor to create a map from the array of key-value pairs.
5. **forEach**: Iterates over the array using `forEach` and assigns each element to a property on an empty object.
6. **for of**: Iterates over the array using `for...of` and assigns each element to a property on an empty object.
7. **for i**: Iterates over the array using `for` with an index variable and assigns each element to a property on an empty object, saving the length of the array as a variable.
8. **for i saved length variable**: Similar to the previous approach, but saves the length of the array as a variable before iterating.

**Library and Special Features**

The benchmark uses the following libraries:

* `Array.from()`: Creates an array from an iterable.
* `Object.fromEntries()`: A modern method for creating an object from key-value pairs.
* `Map()`: Creates a map from key-value pairs.

There are no special features used in this benchmark beyond the standard JavaScript APIs.

**Performance Results**

The performance results show the execution time for each test case on a Chrome 121 browser running on a Mac with an Intel processor. The results are:

1. **Object.fromEntries**: ~271ms
2. **Reduce (reuse object)**: ~15ms
3. **Reduce (creating temporary objects)**: ~122ms
4. **Map**: ~262ms
5. **forEach**: ~2077ms
6. **for of**: ~1461ms
7. **for i**: ~121ms
8. **for i saved length variable**: ~15ms

The results indicate that the `Reduce (reuse object)` approach is the fastest, followed closely by the `Object.fromEntries` method. The other approaches are significantly slower, with the `forEach` and `for of` iterations being the slowest.

In conclusion, this benchmark demonstrates the performance differences between various approaches for converting an array to an object in JavaScript.

Related benchmarks:

Convert Array to Object - Compare all possible4 (version: 0)

Comparing performance of: Object.fromEntries vs Reduce (reuse object) vs Reduce (creating temporary objects) vs Map vs forEach vs for of vs for i vs for i saved length variable

Created: 3 years ago by: Guest

Jump to the latest result

Object.fromEntries

Reduce (reuse object)

Reduce (creating temporary objects)

Map

forEach

for of

for i

for i saved length variable

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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