Benchmark: Map has vs set - MeasureThat.net

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

var i = 0, count = 1000, a;
var map = new Map();

for (i = 0; i < count; i++) {
  if (Math.random() > 0.5) {
    map.set(i, i * i);
  }
}

Tests:

Map 1
for (i = 0; i < count; i++) { map.set(i, i) }
Map 2
for (i = 0; i < count; i++) { map.has(i) }

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Map 2

24K/s

Map 1

23K/s

View exact numbers

✓ Map 2: 23,553 ops/sec
• Map 1: 23,342 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map 1
Map 2

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/140.0.0.0 Safari/537.36

Browser/OS: Chrome 140 on Mac OS X 10.15.7

View result in a separate tab

Map 2

24K/s

Map 1

23K/s

View exact numbers

Test name	Executions per second
✓ Map 2	23,553 Ops/sec
Map 1	23,342 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark you've provided compares two different operations on a JavaScript `Map`, specifically testing the performance of the `set` and `has` methods within a loop. Let's break down what is being tested and analyze the options compared, as well as their pros and cons.

### Description of Tests

1. **Map 1**:
   - **Benchmark Definition**: This test defines a loop that runs `map.set(i, i)` for a range of `count` iterations (from 0 to 999). This means for each iteration, a key-value pair is added to the map.
   - **Purpose**: This operation tests the performance of inserting elements into the `Map`.

2. **Map 2**:
   - **Benchmark Definition**: This test defines a loop that runs `map.has(i)`. This checks if a certain key exists in the map for each iteration.
   - **Purpose**: This operation tests the performance of checking whether a key exists (look-up operation) in the `Map`.

### Performance Metrics

The benchmark results provide the number of executions per second for each test:

- **Map 1 (set operation)**: Approximately 21,788 executions per second.
- **Map 2 (has operation)**: Approximately 18,997 executions per second.

### Pros and Cons of Each Approach

1. **Using `map.set()`**:
   - **Pros**:
     - Efficiently adds elements to the map, allowing for dynamic data storage.
     - The `Map` structure maintains the insertion order of its elements, making it useful for scenarios requiring predictable ordering.
   - **Cons**:
     - This involves memory allocation and potential resizing operations which can slightly impact performance if the map grows significantly.

2. **Using `map.has()`**:
   - **Pros**:
     - Provides a quick way to check for the existence of a key, which can save time in scenarios where lookup is needed without alteration of the map.
     - Fast access times, generally O(1) for both insertion and lookup due to the underlying hash table implementation.
   - **Cons**:
     - If used excessively without prior data optimizations (like pre-computing expected keys), it could add overhead due to repeated checks in a large dataset.

### Other Considerations

- Using a `Map` vs. other data structures (like plain objects or arrays):
  - A `Map` is preferable when you need key-value pairs and require particular features such as maintaining insertion order, or when the keys are not restricted to string type (they can be of any type).
  - Plain objects, while often faster for simple key-value use-cases, do not maintain order and only allow string keys.

- **Alternatives to Maps**:
  - **Objects**: For simple key-value mappings where keys are known to be strings, objects might be used because of their simplicity and slightly better performance in specific contexts.
  - **Sets**: If you only need to store unique values and don’t need key-value pairs, using a `Set` might be appropriate.
  - **Arrays**: For ordered collections of values without unique key constraints, arrays can be employed, but they require different access patterns.

### Summary

This benchmark provides insight into the performance characteristics of `Map` operations in JavaScript, highlighting the differences between setting values in a Map versus checking for the existence of those values. By comparing these two operations, developers can better understand where potential performance bottlenecks may arise in applications where these operations are prevalent.

Map has vs set (version: 1)

Comparing performance of: `Map 1 vs Map 2`

Created: one year ago by: Guest

Go to the latest result

Map 1

Map 2

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

Map has vs set (version: 1)

Comparing performance of: Map 1 vs Map 2

Created: one year ago by: Guest

Go to the latest result

Map 1

Map 2

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

Related benchmarks

Comparing performance of: `Map 1 vs Map 2`