Benchmark: Copy map vs. object

Script Preparation code:

var items = Array.from({
    length: 100000
}, (_, i) => ({
    id: `item-${i}`
}))

var dataObj = {};

items.forEach((item, i) => {
  dataObj[item.id] = {
    start: i * 30,
    end: i * 30 + 30
  }
});

var dataMap = new Map();

items.forEach((item, i) => {
  dataMap.set(item.id, {
    start: i * 30,
    end: i * 30 + 30
  });
});

Tests:

Copy obj
const obj = { ...dataObj };
Copy map
const map = new Map(dataMap);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Copy obj
Copy map

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/123.0.0.0 Safari/537.36

Browser/OS: Chrome 123 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Copy obj	43.2 Ops/sec
Copy map	165.8 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested.

**Benchmark Definition**

The benchmark is designed to compare two approaches for copying data: using an object (`dataObj`) versus using a Map (`dataMap`). The script preparation code creates a large array of objects, `items`, with unique IDs. It then defines two data structures:

1. `dataObj`: an object where each key is an ID from the `items` array, and the corresponding value is another object with `start` and `end` properties.
2. `dataMap`: a Map where each key is an ID from the `items` array, and the corresponding value is another object with `start` and `end` properties.

**Options Compared**

The benchmark compares two options:

1. **Copy obj**: This option involves creating a new object by copying `dataObj`.
2. **Copy map**: This option involves creating a new Map by copying `dataMap`.

**Pros and Cons of Each Approach**

**Copy obj**

Pros:

* Typically faster than working with Maps, as objects are often optimized for fast lookups.
* Can be more memory-efficient, especially for large datasets.

Cons:

* May not perform well if the object is very deeply nested or has a complex structure.
* Requires manual handling of key-value pairs and potential conflicts.

**Copy map**

Pros:

* Efficiently handles large amounts of data with unique keys.
* Provides better performance when working with sparse data (i.e., most values are null or undefined).

Cons:

* May be slower than objects for simple lookups, as Maps require a hash table lookup.
* Requires creating an iterator to iterate over the map's entries.

**Other Considerations**

When choosing between these two approaches, consider the following factors:

* Data structure complexity: If your data is mostly structured and has unique keys, `dataMap` might be a better choice. For more complex or deeply nested data, objects might be more suitable.
* Performance: If you're working with sparse data or need fast lookups, `dataMap` could provide an advantage. However, for dense data or simple lookups, objects are often faster.

**Library and Special JS Features**

In this benchmark, the following libraries/libraries-like-constructs are used:

1. `Array.from()`: creates a new array from an iterable.
2. `Object.assign()` (implied by `const obj = { ...dataObj };`): copies properties from one object to another.

No special JS features or syntax are explicitly mentioned in this benchmark.

**Alternatives**

If you're looking for alternatives to these two approaches, consider the following:

1. **Use a library like Lodash**: provides various utility functions for working with arrays and objects, including `_.map()` and `_.merge()`.
2. **Implement a custom iterator**: if you need fine-grained control over data access or iteration, creating a custom iterator can provide more flexibility.

Keep in mind that these alternatives might introduce additional complexity or performance overhead, so carefully consider your specific use case before choosing an alternative approach.

Related benchmarks:

Copy map vs. object (version: 0)

Comparing performance of: Copy obj vs Copy map

Created: 3 years ago by: Guest

Jump to the latest result

Copy obj

Copy map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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