Benchmark: Object iteration methods

Script Preparation code:

var obj = {};

for(let i = 0; i < 30; ++i) {
	obj['*'+Math.random()] = Math.random();
}

Tests:

for
let x = 0; for(const key in obj) { if(!Object.prototype.hasOwnProperty.call(obj, key)) { continue; } x += obj[key]; }
Object.entries + for
let x = 0; const entries = Object.entries(obj); for(let i=0; i<entries.length; ++i) { x += entries[i][1]; }
Object.entries + forEach
let x = 0; Object.entries(obj).forEach((entry) => { x += entry[1]; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
Object.entries + for
Object.entries + forEach

Fastest: N/A

Slowest: N/A

Latest run results:

No previous 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 dive into the world of JavaScript microbenchmarks.

**What is being tested?**

The provided JSON represents a benchmark for comparing three different approaches to iterate over an object in JavaScript:

1.  **For loop**: A traditional `for` loop using the `in` operator to access object properties.
2.  **Object.entries + For loop**: Using `Object.entries()` to get an array of key-value pairs and then iterating over it with a `for` loop.
3.  **Object.entries + forEach**: Utilizing `Object.entries()` to get an array of key-value pairs and then using the `forEach()` method to iterate over it.

**Options comparison**

These three approaches have different pros and cons:

*   **For Loop**: This is a traditional way of iterating over objects in JavaScript. It's straightforward and works well for simple cases. However, it can be slower than other methods because it involves checking if the property exists using `Object.prototype.hasOwnProperty.call()`, which can lead to a performance hit if the object is very large.
*   **Object.entries + For Loop**: This approach uses the `Object.entries()` method to get an array of key-value pairs and then iterates over it with a traditional `for` loop. It's more efficient than the first option because it avoids the overhead of checking property existence. However, it still requires iteration over the array, which can be slower than other methods.
*   **Object.entries + forEach**: This approach uses the `Object.entries()` method to get an array of key-value pairs and then iterates over it using the `forEach()` method. It's often considered the most efficient option because it leverages the optimized iteration logic provided by modern JavaScript engines.

**Pros and Cons**

*   **For Loop**:
    *   Pros: Easy to understand, straightforward.
    *   Cons: Can be slower due to property existence checks.
*   **Object.entries + For Loop**:
    *   Pros: More efficient than the for loop method, avoids property existence checks.
    *   Cons: Requires iteration over the array, may not be as fast as other methods.
*   **Object.entries + forEach**:
    *   Pros: Often considered the most efficient option, leverages optimized iteration logic.
    *   Cons: May have some additional overhead due to function call and array creation.

**Libraries used**

There are no libraries explicitly mentioned in the provided benchmark code. However, `Object.entries()` is a modern JavaScript method introduced in ECMAScript 2015 (ES6), which provides a convenient way to get an array of key-value pairs from an object.

**Special JS feature/syntax**

The benchmark uses modern JavaScript features such as:

*   **Template literals**: Used for creating the `obj` variable with random property names.
*   **ES6 syntax**: Used for defining arrow functions (e.g., `() => {x += entry[1];}`).
*   **Object.entries() method**: Introduced in ES6, provides an array of key-value pairs from an object.

**Alternatives**

Other alternatives to compare the performance of iterating over objects include:

*   Using `for...of` loop: Instead of using traditional `for` loops with `in`, you can use `for...of` loop with the `entries()` method.
*   Using `Map` data structure: If you need to iterate over object properties frequently, using a `Map` data structure might be more efficient than objects.
*   Using other iteration methods: Depending on your specific requirements, other iteration methods like `reduce()`, `forEachArray()`, or `map()` might be more suitable.

Related benchmarks:

Object iteration methods (version: 0)

Comparing performance of: for vs Object.entries + for vs Object.entries + forEach

Created: 6 years ago by: Guest

Jump to the latest result

for

Object.entries + for

Object.entries + forEach

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):