Benchmark: Object spread vs New map entries

Script Preparation code:

var data = new Array(100000).fill(undefined).map((_,i) => i)
var obj = data.reduce((obj, idx) => {obj[idx] = idx; return obj}, {});
var map = new Map(Object.entries(obj));

Tests:

Obj spread
let a = {...obj};
new Map
let a = new Map([...map.entries()]);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Obj spread
new Map

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

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Let's break down the provided JSON benchmark definition and test cases.

**Benchmark Definition:**

The provided JSON represents a JavaScript microbenchmark that compares two approaches to creating objects from an existing object:

1. **Object Spread**: Using the spread operator (`...`) to create a new object with entries from the original object.
2. **New Map Entries**: Creating a new Map instance and adding entries using `Map` constructor, which takes an array of key-value pairs.

**Script Preparation Code:**

The script preparation code is used to set up the environment for the benchmark:
```javascript
var data = new Array(100000).fill(undefined).map((_,i) => i)
var obj = data.reduce((obj, idx) => {obj[idx] = idx; return obj}, {})
var map = new Map(Object.entries(obj))
```
This code creates an array of 100,000 elements with indices from 0 to 99,999. It then reduces the array into a single object using the `reduce` method and assigns each index as its corresponding value.

**HTML Preparation Code:**

There is no HTML preparation code provided, which means that this benchmark only tests JavaScript engine behavior and does not involve any DOM-related operations.

**Test Cases:**

The individual test cases are defined in the "Benchmark Definition" section:
```javascript
[
  {
    "Benchmark Definition": "let a = {...obj};",
    "Test Name": "Obj spread"
  },
  {
    "Benchmark Definition": "let a = new Map([...map.entries()]);",
    "Test Name": "new Map"
  }
]
```
These test cases create a new object by spreading the `obj` object and assigning it to variable `a`. The second test case creates a new Map instance from the entries of the original `map` object.

**Library:**

The `Map` data structure is a built-in JavaScript library, introduced in ECMAScript 2015 (ES6). It provides a way to store key-value pairs and allows efficient lookup, insertion, and deletion of elements.

**Special JS Features/Syntax:**

* The spread operator (`...`) is used in the "Obj spread" test case. This feature was introduced in ES6 and allows creating new objects by spreading existing objects.
* The `Map` constructor is also part of the ES6 standard.

**Options Compared:**

The benchmark compares two options for creating a new object:

1. **Object Spread**: Using the spread operator to create a new object with entries from the original object.
2. **New Map Entries**: Creating a new Map instance and adding entries using `Map` constructor, which takes an array of key-value pairs.

**Pros and Cons:**

* **Object Spread**:
	+ Pros: Fast, lightweight, and easy to implement.
	+ Cons: May not be as efficient for large datasets due to the overhead of object creation.
* **New Map Entries**:
	+ Pros: Efficient for large datasets, allows for fast lookup and insertion of elements.
	+ Cons: Requires additional memory and can be more complex to implement.

**Other Alternatives:**

If you want to test other approaches to creating objects, here are some alternatives:

1. Using the `Object.assign()` method to create a new object by assigning entries from an existing object.
2. Creating a new object using the `{}` syntax with key-value pairs assigned directly.
3. Using a library like Lodash's `_.cloneDeep()` function to clone an existing object.

These alternatives can be tested in additional benchmark cases, allowing for more comprehensive testing of JavaScript engine behavior and performance characteristics.

Related benchmarks:

Object spread vs New map entries (version: 0)

Comparing performance of: Obj spread vs new Map

Created: 3 years ago by: Guest

Jump to the latest result

Obj spread

new Map

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):