Benchmark: Map vs Object (large)

Script Preparation code:

var map = new Map();
var obj = {};
obj['b'] = 5;
delete obj['b'];

for (var x = 0; x < 1000; x++) {
  map.set("x" + x, x);
  obj["x" + x] = x;
}
map.set('a', 5);
obj['a'] = 5;

var i = 0, count = 10, a;

Tests:

Map lookup
for (i = 0; i < count; i++) { a = map.get('a'); }
Obj lookup
for (i = 0; i < count; i++) { a = obj['a']; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map lookup
Obj lookup

Fastest: N/A

Slowest: N/A

Latest run results:

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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 to understand what is being tested and the different approaches compared.

**Benchmark Definition**

The benchmark measures the performance of two different data structures in JavaScript: Maps (`map`) and objects (`obj`). The test case "Map vs Object (large)" creates a large dataset by:

1. Creating an empty Map and object.
2. Deleting a key from the object to simulate a lookup failure.
3. Populating both the Map and object with 1000 entries using a loop, where each entry sets a key-value pair in both data structures.
4. Adding two more key-value pairs to both data structures.

**Options Compared**

The benchmark compares the performance of two approaches:

1. **Map Lookup**: Using the `map.get()` method to retrieve values from the Map.
2. **Object Lookup**: Using the bracket notation (`obj['a']`) to access values in the object.

**Pros and Cons of Each Approach**

* **Map Lookup (get())**:
	+ Pros: Maps are optimized for fast lookups, especially when dealing with large datasets. `map.get()` is a single-step operation that directly returns the value associated with the given key.
	+ Cons: Maps are designed to be mutable, and when accessed in a sequential manner like this test case, they can lead to cache misses, which impact performance.
* **Object Lookup (bracket notation)**:
	+ Pros: Objects are more familiar to developers, and bracket notation is often considered more readable. It's also generally faster than `map.get()` for simple lookups.
	+ Cons: Object lookups can be slower when dealing with large datasets, especially if the keys are not contiguous in memory.

**Special Considerations**

The test case uses a special JavaScript feature: **`let` and `const` declarations**, which were introduced in ECMAScript 2015 (ES6). The use of these keywords helps prevent the `var` hoisting behavior, making the code more predictable and easier to maintain.

**Library Used**

There is no explicit library used in this benchmark. However, it's worth noting that some browsers may have additional optimizations or features for Maps or objects that might affect the results.

**Alternatives**

Other alternatives for achieving fast lookups in JavaScript include:

1. **Using `WeakMap`**: A `WeakMap` is a Map implementation that only stores weak references to keys, which can help reduce memory usage.
2. **Using `Object.prototype.hasOwnProperty.call()`**: This method checks if an object has a property with the given name without throwing an error if it's missing.
3. **Using a data structure like a Trie or a Hash Table**: These data structures are optimized for fast lookups and might provide better performance in certain scenarios.

Keep in mind that the choice of approach depends on the specific use case, requirements, and constraints of your application.

Related benchmarks:

Map vs Object (large) (version: 0)

Lookup of map vs object

Comparing performance of: Map lookup vs Obj lookup

Created: 5 years ago by: Guest

Jump to the latest result

Map lookup

Obj lookup

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):