Benchmark: Map vs WeakMap (real-world) Performance

Script Preparation code:

var keyCount = 16384
var keys = []
var map = new Map()
var weakmap = new WeakMap()


// Hide lookup keys to prevent V8 cheating (AKA Optimizing)
var getConspicuousKey = seed => keys[Math.floor(seed * keyCount)]


// Setup out test objects w/ random values
for (let i=0; i<keyCount; i++) {
  let val = Math.random()
  let key = {}
  keys.push(key)
  map.set(key,val)
  weakmap.set(key,val)
}

Tests:

Conspicuous Map lookup
for (let i=0; i<keyCount; i++) { let seed = Math.random() let key = getConspicuousKey(seed) a = map.get(key) }
Conspicuous WeakMap lookup
for (let i=0; i<keyCount; i++) { let seed = Math.random() let key = getConspicuousKey(seed) a = weakmap.get(key) }
Conspicuous Map lookup 2
for (let i=0; i<keyCount; i++) { let seed = Math.random() let key = getConspicuousKey(seed) a = map.get(key) }
Conspicuous WeakMap lookup 2
for (let i=0; i<keyCount; i++) { let seed = Math.random() let key = getConspicuousKey(seed) a = weakmap.get(key) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Conspicuous Map lookup
Conspicuous WeakMap lookup
Conspicuous Map lookup 2
Conspicuous WeakMap lookup 2

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Measuring the performance of different data structures in JavaScript, such as `Map` and `WeakMap`, is crucial for optimizing applications.

**Benchmark Definition**

The benchmark tests the performance of looking up values in a `Map` versus a `WeakMap`. A `Map` is an object that stores key-value pairs, while a `WeakMap` is similar but allows keys to be garbage collected when they are no longer referenced.

**Options Compared**

Two options are compared:

1. **`Map` lookup**: This option uses the `get()` method of the `Map` interface to retrieve values based on their keys.
2. **`WeakMap` lookup**: This option uses the `get()` method of the `WeakMap` interface to retrieve values based on their keys.

**Pros and Cons**

* **`Map`**:
	+ Pros: Can be used with any type of key, including non-primitive values like objects and arrays.
	+ Cons: Memory-intensive because it stores all keys in memory, even if they are no longer referenced. This can lead to performance issues if the map grows too large.
* **`WeakMap`**:
	+ Pros: Can help prevent memory leaks by allowing keys to be garbage collected when they are no longer referenced.
	+ Cons: Requires a reference to the key object to retrieve its value, which can lead to slower lookup times.

**Library**

In this benchmark, neither `Map` nor `WeakMap` use any external libraries. They are built-in JavaScript data structures.

**Special JS Feature/Syntax**

This benchmark uses some advanced JavaScript features:

* **Template literals**: Used in the `getConspicuousKey()` function to generate a random key.
* **Arrow functions**: Used in the `for...of` loops to define small anonymous functions.
* **Computed property names**: Used in the `map` and `weakmap` objects to create computed properties.

However, these features are not specific to JavaScript and are widely used in many programming languages.

**Other Alternatives**

If you're interested in comparing performance between different data structures in JavaScript, here are some alternatives:

* **`Set` vs `WeakSet`**: Compare the performance of looking up values in a `Set` versus a `WeakSet`.
* **`Array` vs `Int8Array`**: Compare the performance of accessing elements in an `Array` versus an `Int8Array`.
* **`JSON.parse()` vs `JSON.stringify()```**: Compare the performance of parsing JSON strings using `JSON.parse()` versus stringifying JSON objects using `JSON.stringify()`.

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36

Browser/OS: Chrome 124 on Windows

View result in a separate tab

Test name	Executions per second
Conspicuous Map lookup	44.2 Ops/sec
Conspicuous WeakMap lookup	46.0 Ops/sec
Conspicuous Map lookup 2	44.6 Ops/sec
Conspicuous WeakMap lookup 2	46.4 Ops/sec

Related benchmarks:

Map vs WeakMap (real-world) Performance (version: 0)

Lookup of map vs object (in a real-world test format)

Comparing performance of: Conspicuous Map lookup vs Conspicuous WeakMap lookup vs Conspicuous Map lookup 2 vs Conspicuous WeakMap lookup 2

Created: 2 years ago by: Guest

Jump to the latest result

Conspicuous Map lookup

Conspicuous WeakMap lookup

Conspicuous Map lookup 2

Conspicuous WeakMap lookup 2

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):