Benchmark: Map vs Object - Dynamic keys

Script Preparation code:

var map = new Map();
var obj = {};

map.set('1', 5);
obj['1'] = 5;

var i = 0, count = 1000, a, index;

Tests:

Map
index = 1; for (i = 0; i < count; i++) { if(!map.has(index +'')) { map.set(index + '', 5); } a = map.get(index + ''); index++; index = index === 100 ? 1 : index; }
Obj
index = 1; for (i = 0; i < count; i++) { if(!obj.hasOwnProperty(index +'')) { obj[index + ''] = 5; } a = obj[index + '']; index++; index = index === 100 ? 1 : index; }
Obj - for in
index = 1; for (i = 0; i < count; i++) { if(!(index + i in obj)) { obj[index + ''] = 5; } a = obj[index + '']; index++; index = index === 100 ? 1 : index; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map
Obj
Obj - for in

Fastest: N/A

Slowest: N/A

Latest run results:

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

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I'll break down the provided benchmark and its options, highlighting their pros and cons.

**Benchmark Overview**

The benchmark compares three approaches to dynamically set keys on an object:

1.  **Map**: Using JavaScript's built-in `Map` data structure with dynamic key generation using the `has()` method.
2.  **Object**: Using a plain JavaScript object (`obj`) with dynamic key generation using the `.hasOwnProperty()` method.
3.  **For-in loop**: Using a for-in loop to dynamically set keys on an object, which is not as efficient as the first two approaches.

**Library Usage**

The benchmark uses the following libraries:

*   None explicitly mentioned. However, it's worth noting that JavaScript engines might use some underlying libraries or optimizations during execution.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark. The focus is on comparing the efficiency of different approaches to dynamically set keys on objects.

**Benchmark Options and Approaches**

Here's a brief overview of each option:

1.  **Map**: Using `Map` provides efficient key generation and lookup using the `has()` method, which has an average time complexity of O(1). This approach is suitable for large datasets.
    *   Pros: Fast lookups and insertions, good cache locality.
    *   Cons: May require additional memory allocation for the `Map` object.

2.  **Object**: Using a plain JavaScript object (`obj`) with dynamic key generation using `hasOwnProperty()` has an average time complexity of O(1) as well. However, it's less efficient than `Map` due to slower lookup times compared to its own data structure.
    *   Pros: Fast lookups and insertions, doesn't require additional memory allocation.
    *   Cons: May be slower for large datasets.

3.  **For-in loop**: Using a for-in loop is the least efficient of the three approaches. It iterates over all enumerable properties of an object and checks if the generated key exists in the object using `in`. This approach has an average time complexity of O(n), where n is the number of iterations.
    *   Pros: None notable.
    *   Cons: Slow lookup times, potential for iterating over unnecessary properties.

**Other Alternatives**

There are other alternatives to these approaches that could be considered:

*   **WeakMap**: Using a `WeakMap` might provide better performance than `Object` due to its ability to optimize garbage collection. However, it's less suitable for this specific use case.
*   **Proxy**: Using proxies might allow for more control over key generation and lookup. However, it adds additional complexity compared to the existing approaches.

Keep in mind that these alternatives are not part of the original benchmark but could be considered when building similar benchmarks or optimizing code.

Related benchmarks:

Map vs Object - Dynamic keys (version: 0)

Lookup of map vs object with dynamic keys

Comparing performance of: Map vs Obj vs Obj - for in

Created: 3 years ago by: Registered User

Jump to the latest result

Map

Obj

Obj - for in

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):