Benchmark: Index method vs Object.values

Script Preparation code:

var data = Array(10000).fill(null).map((x, i) => ({ x: i }));

Tests:

Index method
var index = {}; var arr = []; data.forEach((x) => { if (!x.x in index) { arr.push(x); index[x.x] = arr.length - 1; } });
Object method
var indexedObject = data.reduce((acc, x) => { if (!x.x in acc) acc[x.x] = x; return acc; }, {}); var arr = Object.values(indexedObject);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Index method
Object method

Fastest: N/A

Slowest: N/A

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

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

**What is being tested?**

The benchmark measures the performance of two different approaches to iterate over an array of objects:

1. **Index method**: This approach uses a nested `forEach` loop with an index variable (`x`) to access each object in the array.
2. **Object method**: This approach uses the `Object.values()` method, which returns an array of values for the given object.

**Options being compared**

The benchmark is comparing the performance of these two approaches on a dataset consisting of 10,000 objects with unique keys (i.e., no duplicate keys).

**Pros and cons of each approach:**

1. **Index method**:
	* Pros:
		+ Low-level control over iteration.
		+ Might be more efficient for small to medium-sized datasets.
	* Cons:
		+ Requires explicit indexing, which can lead to errors if not done correctly.
		+ May not be as cache-friendly as the object method.
2. **Object method**:
	* Pros:
		+ Cache-friendly, as `Object.values()` uses a hash table internally.
		+ Less error-prone than the index method.
	* Cons:
		+ Requires the use of an external method (`Object.values()`), which might incur additional overhead.
		+ May be slower for very large datasets due to the creation of an intermediate array.

**Library and its purpose**

In this benchmark, `Array.prototype.forEach()` is used as a library function. It's a built-in method in JavaScript that allows you to iterate over arrays in a predictable way.

**Special JS feature or syntax (not applicable)**

There are no special features or syntaxes being tested in this benchmark.

**Other alternatives**

For iterating over arrays of objects, other approaches include:

1. `for...in` loop: This approach iterates over the object's properties using the `in` operator. While it's not as cache-friendly as the object method, it can be useful for certain use cases.
2. `for...of` loop (ECMAScript 2015+): This approach is similar to the index method but uses a more modern and concise syntax.

In summary, the benchmark measures the performance of two approaches to iterate over an array of objects: the index method and the object method using `Object.values()`. The choice between these approaches depends on the specific use case, dataset size, and desired trade-offs between control, cache-friendliness, and overhead.

Related benchmarks:

Index method vs Object.values (version: 0)

Comparing performance of: Index method vs Object method

Created: 5 years ago by: Guest

Jump to the latest result

Index method

Object method

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):