Benchmark: For in vs Object.*.forEach vs Object.values vs Object.values in for loop

Script Preparation code:

var obj = new Object()
var keys = (new Array(10000)).fill(0).map((x, i) => { return i + 1 })
keys.forEach((x) => { obj['prop' + x] = x })

Tests:

For In
for (var key in obj) { console.log(obj[key]); }
Object values
for(let value of Object.values(obj)){ console.log(value); }
Object keys forEach
Object.keys(obj).forEach(key => console.log(obj[key]));
Object entries forEach
Object.entries(obj).forEach(([key, value]) => console.log(key,'->',value));
object values forEach
Object.values(obj).forEach(value => console.log(value));
Object entries plus for loop
let values = Object.values(obj) let length = values.length for(let i = 0; i < length; i++){ console.log(values[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For In
Object values
Object keys forEach
Object entries forEach
object values forEach
Object entries plus for loop

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 JavaScript microbenchmark and analyze what is being tested.

**Benchmark Definition**

The benchmark definition specifies that we are comparing different approaches to iterate over an object's properties:

1. **For In**: Using `for (var key in obj)` to iterate over the object's own enumerable properties.
2. **Object.values**: Using `for(let value of Object.values(obj))` to iterate over the object's values as an array.
3. **Object.keys** and **forEach**: Using `Object.keys(obj).forEach(key => console.log(obj[key]))` to iterate over the object's keys as an array using `forEach`.
4. **Object.entries** and **forEach**: Using `Object.entries(obj).forEach(([key, value]) => console.log(key,'->',value))` to iterate over the object's key-value pairs as an array of tuples using `forEach`.
5. **Object values** with a custom loop: Using a manual loop with `Object.values(obj)` to iterate over the object's values.

**Options Comparison**

The options being compared are:

*   **For In**: Iterates over the object's properties, but can lead to slower performance due to the use of the `in` operator.
*   **Object.values**: Iterates over the object's values as an array, which can be more efficient since arrays are optimized for iteration. However, it does not provide direct access to the keys.
*   **Object.keys** and **forEach**: Iterates over the object's keys as an array using `forEach`. This approach is similar to `Object.values`, but with a different data structure.
*   **Object.entries** and **forEach**: Iterates over the object's key-value pairs as an array of tuples using `forEach`. This approach provides direct access to both keys and values.

**Pros and Cons**

Here are some pros and cons for each approach:

*   **For In**:
    *   Pros: Can be more intuitive and easier to understand, especially when dealing with objects that have a natural iteration order (e.g., object properties in a specific order).
    *   Cons: Can lead to slower performance due to the use of the `in` operator.
*   **Object.values**:
    *   Pros: Can be more efficient since arrays are optimized for iteration, and provides direct access to the values.
    *   Cons: Does not provide direct access to the keys.
*   **Object.keys** and **forEach**:
    *   Pros: Provides direct access to the keys, similar to `Object.entries`. The `forEach` approach can be more efficient than a custom loop with `Object.values`.
    *   Cons: Requires an additional step to get the values using indexing or another method.
*   **Object entries** and **forEach**:
    *   Pros: Provides direct access to both keys and values, which can be beneficial in certain scenarios. The `forEach` approach can be more efficient than a custom loop with `Object.values`.
    *   Cons: May require additional processing to extract the values from the tuples.

**Other Considerations**

When choosing an iteration approach, consider the following factors:

*   **Performance**: Object iteration approaches using arrays (e.g., `Object.values`, `Object.keys` and `forEach`) are generally more efficient than those using objects with `in`.
*   **Readability and maintainability**: Choose an approach that is easy to understand and maintain. `For In` can be more intuitive for simple use cases, while object iteration approaches using arrays might require additional consideration for readability.
*   **Accessing keys and values**: Depending on your requirements, you may need direct access to both keys and values. Object iteration approaches with `Object.entries` or `Object.keys` and `forEach` provide this.

**Library Use**

The benchmark uses the following libraries:

*   **None explicitly mentioned**, but it is assumed that the JavaScript runtime environment provides the necessary functionality for these tests.

No special JavaScript features or syntax are used in this benchmark.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Windows

View result in a separate tab

Test name	Executions per second
For In	18.5 Ops/sec
Object values	18.4 Ops/sec
Object keys forEach	20.1 Ops/sec
Object entries forEach	15.1 Ops/sec
object values forEach	21.3 Ops/sec
Object entries plus for loop	19.8 Ops/sec

Related benchmarks:

For in vs Object.*.forEach vs Object.values vs Object.values in for loop (version: 0)

Comparing performance of: For In vs Object values vs Object keys forEach vs Object entries forEach vs object values forEach vs Object entries plus for loop

Created: one year ago by: Guest

Jump to the latest result

For In

Object values

Object keys forEach

Object entries forEach

object values forEach

Object entries plus for loop

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):