Benchmark: Map vs object copying

Script Preparation code:

var objects = []
var maps = []

for (let i = 0; i < 100; i++) {
  const obj = {};
  const map = new Map()
  for (let j = 0; j < 10; j++) {
    const propName = Math.random().toString(36).substr(2, 10); // Generate a random 10-character string
    const propValue = Math.floor(Math.random() * 1000); // Generate a random integer between 0 and 999

    obj[propName] = propValue;
    map.set(propName, propValue);
  }

  objects.push(obj);
  maps.push(map);
}

​x
 
var objects = []var maps = []​for (let i = 0; i < 100; i++) {  const obj = {};  const map = new Map()  for (let j = 0; j < 10; j++) {    const propName = Math.random().toString(36).substr(2, 10); // Generate a random 10-character string    const propValue = Math.floor(Math.random() * 1000); // Generate a random integer between 0 and 999​    obj[propName] = propValue;    map.set(propName, propValue);  }​  objects.push(obj);  maps.push(map);}​​

Tests:

Copy objects
const new_objects = objects.map( (obj) => { return {...obj} })
const new_objects = objects.map( (obj) => {
return {...obj}
})
Copy maps
const new_maps = maps.map( (m) => { return new Map(m); })
const new_maps = maps.map( (m) => {
return new Map(m);
})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Experimental features:

Memory measurements supported only in Chrome.
For precise memory measurements Chrome must be launched with --enable-precise-memory-info flag.
More information: Monitoring JavaScript Memory

Test case name	Result
Copy objects
Copy maps

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/111.0.0.0 Safari/537.36

Browser/OS: Chrome 111 on Windows

View result in a separate tab

Test name	Executions per second
Copy objects	50802.9 Ops/sec
Copy maps	15737.3 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

Measuring the performance of different approaches in JavaScript is crucial to optimizing code and improving application performance.

The provided benchmark measures two approaches for creating copies of objects and maps:

Approach 1: objects.map((obj) => {...obj})

This approach uses the Array.prototype.map() method, which returns a new array with the results of applying the provided function to each element in the original array. The lambda function (obj) => {...obj} creates a new object by spreading the properties of the original object (obj) into a new object.

Approach 2: maps.map((m) => new Map(m))

This approach uses the Array.prototype.map() method, similar to Approach 1. However, instead of mapping over an array, it maps over a collection of Maps (in this case, just one map). The lambda function (m) => new Map(m) creates a new Map by iterating over the key-value pairs of the original map (m) and adding them as entries to the new map.

Comparison

Both approaches create new objects and maps that contain the same properties and values as the originals. However, there are some differences:

Memory allocation: Approach 1 may allocate more memory because it creates a new array with a copy of each object, whereas Approach 2 creates a new Map, which is an optimized data structure for storing key-value pairs.
Iteration: Approach 2 requires iterating over the key-value pairs of the original map to create the new map, whereas Approach 1 only iterates over the objects in the array.

Pros and Cons

Approach 1 (objects.map((obj) => {...obj})) Pros:

Easy to read and write
Can be used for other data structures (e.g., arrays)

Cons:

May allocate more memory than Approach 2
Iterates over objects in the array, not key-value pairs

Approach 2 (maps.map((m) => new Map(m))) Pros:

Optimized for storing key-value pairs
Creates a new Map that contains the same data as the original map

Cons:

More complex to read and write
Requires iterating over key-value pairs in the map

Other Considerations

In general, Approach 2 (maps.map((m) => new Map(m))) is more efficient than Approach 1 (objects.map((obj) => {...obj})) because it creates an optimized data structure (a Map) that contains the same data as the original map. However, Approach 1 may be easier to understand and implement for simple cases.

Libraries Used

None are explicitly mentioned in the provided benchmark definition or test cases.

Special JS Features/Syntax

None are explicitly used in the provided benchmark definition or test cases.

Alternatives

Other approaches for creating copies of objects and maps include:

Using Object.assign() to create a shallow copy of an object
Using Array.prototype.reduce() to create a deep copy of an array
Using a library like Lodash's cloneDeep() function to create a deep copy of an object or array

Note that these alternatives may have different performance characteristics and trade-offs compared to the approaches measured in this benchmark.

LLMs can make mistakes. Check important info.

Measuring the performance of different approaches in JavaScript is crucial to optimizing code and improving application performance.

The provided benchmark measures two approaches for creating copies of objects and maps:

**Approach 1: `objects.map((obj) => {...obj})`**

This approach uses the `Array.prototype.map()` method, which returns a new array with the results of applying the provided function to each element in the original array. The lambda function `(obj) => {...obj}` creates a new object by spreading the properties of the original object (`obj`) into a new object.

**Approach 2: `maps.map((m) => new Map(m))`**

This approach uses the `Array.prototype.map()` method, similar to Approach 1. However, instead of mapping over an array, it maps over a collection of Maps (in this case, just one map). The lambda function `(m) => new Map(m)` creates a new Map by iterating over the key-value pairs of the original map (`m`) and adding them as entries to the new map.

**Comparison**

Both approaches create new objects and maps that contain the same properties and values as the originals. However, there are some differences:

* **Memory allocation**: Approach 1 may allocate more memory because it creates a new array with a copy of each object, whereas Approach 2 creates a new Map, which is an optimized data structure for storing key-value pairs.
* **Iteration**: Approach 2 requires iterating over the key-value pairs of the original map to create the new map, whereas Approach 1 only iterates over the objects in the array.

**Pros and Cons**

**Approach 1 (`objects.map((obj) => {...obj})`)**
Pros:

* Easy to read and write
* Can be used for other data structures (e.g., arrays)

Cons:

* May allocate more memory than Approach 2
* Iterates over objects in the array, not key-value pairs

**Approach 2 (`maps.map((m) => new Map(m))`)**
Pros:

* Optimized for storing key-value pairs
* Creates a new Map that contains the same data as the original map

Cons:

* More complex to read and write
* Requires iterating over key-value pairs in the map

**Other Considerations**

In general, Approach 2 (`maps.map((m) => new Map(m))`) is more efficient than Approach 1 (`objects.map((obj) => {...obj})`) because it creates an optimized data structure (a Map) that contains the same data as the original map. However, Approach 1 may be easier to understand and implement for simple cases.

**Libraries Used**

None are explicitly mentioned in the provided benchmark definition or test cases.

**Special JS Features/Syntax**

None are explicitly used in the provided benchmark definition or test cases.

**Alternatives**

Other approaches for creating copies of objects and maps include:

* Using `Object.assign()` to create a shallow copy of an object
* Using `Array.prototype.reduce()` to create a deep copy of an array
* Using a library like Lodash's `cloneDeep()` function to create a deep copy of an object or array

Note that these alternatives may have different performance characteristics and trade-offs compared to the approaches measured in this benchmark.

Related benchmarks:

Map vs object copying (version: 0)

Comparing performance of: Copy objects vs Copy maps

Created: 2 years ago by: Registered User

Jump to the latest result

Copy objects

Copy maps

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):