Benchmark: for object - MeasureThat.net

Script Preparation code:

var object = Object.fromEntries(Array(1000).fill().map(() => [Math.random(), Math.random()]));
var t;

Tests:

forEach over entries
Object.entries(object).forEach((v, k) => { t = v })
for of over entires
for (const [v, k] of Object.entries(object)) { t = v }
forEach over values
Object.values(object).forEach((v) => { t = v })
for of over values
for (const v of Object.values(object)) { t = v }
forEach over keys
Object.keys(object).forEach((k) => { t = object[k] })
for of over keys
for (const k of Object.keys(object)) { t = object[k] }
for in
for (const k in object) { t = object[k] }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach over entries
for of over entires
forEach over values
for of over values
forEach over keys
for of over keys
for in

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases.

**Benchmark Overview**

The benchmark is designed to compare the performance of different loop constructs in JavaScript: `for...of`, `forEach`, and `for...in`. The script preparation code creates an object with 1000 entries, each containing a random key-value pair. The html preparation code is null, indicating that no HTML-related code is executed.

**Loop Constructs Compared**

The benchmark compares the performance of three loop constructs:

1. **`for...of`**: This construct iterates over the values of an array-like object (in this case, `Object.entries(object)`). It's used to iterate directly over the values or keys without having to access the property using bracket notation.
2. **`forEach`**: This is a method that executes a callback function once for each element in an array-like object. It's commonly used to iterate over arrays or objects.
3. **`for...in`**: This construct iterates over the properties of an object (including its keys) and returns them in sequence.

**Pros and Cons of Each Approach**

*   `for...of`:
    *   Pros: More concise and expressive, directly iterating over values or keys without bracket notation.
    *   Cons: Not suitable for all types of data structures, like arrays with index-based access.
*   `forEach`:
    *   Pros: Widely supported and versatile, works well with both arrays and objects. It's often used when you need to execute a function on each element in an array or object.
    *   Cons: Not as efficient as `for...of`, as it involves additional overhead due to method invocation.
*   `for...in`:
    *   Pros: Allows iteration over both keys and values, suitable for objects. However, be cautious when using this loop construct, as it can also iterate over inherited properties if not used carefully.
    *   Cons: Less concise than the other two options, often requires additional logic to access property values directly.

**Additional Considerations**

*   **Iteration Order**: When iterating over an object, the order of iteration might be different depending on the JavaScript engine or browser. This is especially true for objects with inherited properties, as `for...in` can include these in its iteration.
*   **Property Access**: In the context of this benchmark, accessing a property using bracket notation (`object[k]`) is less efficient than directly iterating over keys.

**Alternative Approaches**

For comparing performance or optimizing loop constructs:

1.  **Using `Array.prototype.map()` instead of `for` loops**: When working with arrays and performing operations on each element, consider using `map()`. This can often provide better performance due to its optimized implementation.
2.  **Profiling**: Use a profiling tool (e.g., Chrome DevTools' Profiler) to identify specific bottlenecks in your code and optimize those areas.

Keep in mind that performance optimization should always be guided by the specific requirements of your application, taking into account factors like memory usage, readability, and maintainability.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.5.2 Safari/605.1.15

Browser/OS: Safari 16 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
forEach over entries	13660.1 Ops/sec
for of over entires	10022.4 Ops/sec
forEach over values	21077.5 Ops/sec
for of over values	21209.2 Ops/sec
forEach over keys	9877.1 Ops/sec
for of over keys	9966.6 Ops/sec
for in	11717.1 Ops/sec

Related benchmarks:

for object (version: 0)

Compare loop performance

Comparing performance of: forEach over entries vs for of over entires vs forEach over values vs for of over values vs forEach over keys vs for of over keys vs for in

Created: one year ago by: Registered User

Jump to the latest result

forEach over entries

for of over entires

forEach over values

for of over values

forEach over keys

for of over keys

for in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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