Benchmark: dict-iteration - MeasureThat.net

Tests:

Always get keys
let testDict = {}; for (let i = 0; i < 1000; i++) { testDict["key" + i] = 1; } let sum = 0; for (let i=0; i < Object.keys(testDict).length; i++) { sum += testDict[Object.keys(testDict)[i]] }
Get keys once
let testDict = {}; for (let i = 0; i < 1000; i++) { testDict["key" + i] = 1; } let sum = 0; let obKeys = Object.keys(testDict); for (let i=0; i < obKeys.length; i++) { sum += testDict[obKeys[i]] }
Iterating using "In"
let testDict = {}; for (let i = 0; i < 1000; i++) { testDict["key" + i] = 1; } let sum = 0; for (const testKey in testDict) { sum += testDict[testKey] }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Always get keys
Get keys once
Iterating using "In"

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36

Browser/OS: Chrome 115 on Linux

View result in a separate tab

Test name	Executions per second
Always get keys	22.9 Ops/sec
Get keys once	8802.1 Ops/sec
Iterating using "In"	8809.6 Ops/sec

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 Definition JSON**

The provided JSON represents a benchmark definition, which is essentially a script that defines how to run a microbenchmark. In this case, there are no actual script preparation or HTML preparation codes, indicating that only JavaScript code needs to be executed.

**Test Cases**

There are three individual test cases:

1. **"Always get keys"`**

This test case iterates over the object's properties using `for (const key in testDict)` and adds up their values. This approach has a potential performance issue because it creates an array of keys (`Object.keys(testDict)`) and then iterates over this array, which can be slower than iterating directly over the object's own enumerable properties.

Pros: Simple to implement.

Cons:

* Can be slower due to the extra iteration step.
* Requires additional memory allocation for the `obKeys` variable.

2. **"Get keys once"`**

This test case iterates over the object's properties using `Object.keys(testDict)` and then uses this array to iterate over the object's values, adding them up. This approach avoids creating a new array of keys but still requires an extra iteration step.

Pros: Reduces memory allocation compared to "Always get keys".

Cons:

* Still requires additional memory allocation for the `obKeys` variable.
* Can be slower due to the extra iteration step.

3. **"Iterating using \"In\""`**

This test case uses the `for...in` loop to iterate over the object's own enumerable properties (`testDict`) and adds up their values directly without creating any additional arrays or variables. This approach is often considered faster because it avoids unnecessary overhead like array creation.

Pros: Fastest of the three approaches, as it doesn't create any additional arrays or variables.

Cons:

* Requires understanding of how `for...in` loops work.
* Can be less readable for some developers who are not familiar with this syntax.

**Library: None**

There is no library used in these test cases. The code snippet relies on built-in JavaScript features like `Object.keys()`, `for...in` loops, and array indexing.

**Special JS Feature/ Syntax:** "In" (used in the third test case)

The `for...in` loop uses a non-standard feature called "iteration over property names" that allows iterating directly over an object's own enumerable properties without needing to access them as values. This syntax is not part of standard JavaScript but has been widely adopted.

**Alternatives**

For this specific use case, the three approaches have different trade-offs:

* **Using `Object.keys()`**: Requires creating an extra array and then iterating over it.
* **Using `for...in` loops**: Avoids additional memory allocation but still requires an extra iteration step.
* **Iterating directly over object properties**: Fastest approach, as it avoids unnecessary overhead like array creation.

If you need to iterate over objects in a performance-critical path, using the third approach (iterating directly over object properties) is generally recommended. However, if readability or maintainability are more important than raw performance, the first two approaches might be suitable depending on your specific use case and requirements.

Related benchmarks:

dict-iteration (version: 0)

Comparing performance of: Always get keys vs Get keys once vs Iterating using "In"

Created: one year ago by: Guest

Jump to the latest result

Always get keys

Get keys once

Iterating using "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):