Benchmark: object keys vs loop

Script Preparation code:

var a = [{"id":7,"h":76},{"id":4,"h":34},{"id":9,"h":89}];
var d = [];

Tests:

fori
for(var i=0;i<a.length;i++)d.push(a[i].id);
forin
for(var i in a)d.push(i.id);
foreach
a.forEach((i)=>d.push(i.id));
backwhile
var i = a.length; while(--i)d.push(a[i].id);
forcachelen
var z = a.length; for(var i=0;i<z;i++)d.push(a[i].id);
4of
for(var i of a)d.push(i.id);
backfor
for(var i=a.length-1;i>=0;i--)d.push(a[i].id);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
fori
forin
foreach
backwhile
forcachelen
4of
backfor

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

I'll break down the test cases and explain what's being tested, comparing different approaches, pros and cons of each, and other considerations.

**Benchmark Definition JSON**

The benchmark definition is a JavaScript snippet that defines an array `a` with some objects containing `id` and `h` properties. The script also initializes an empty array `d`.

**Individual Test Cases**

Each test case is defined by a "Benchmark Definition" string, which represents the code snippet to be executed on the array `a`. The test cases are:

1. `for(var i=0;i<a.length;i++)d.push(a[i].id);` - for loop with index-based iteration
2. `for(var i in a)d.push(i.id);` - for loop with object property iteration (using `in`)
3. `a.forEach((i)=>d.push(i.id));` - array method with callback function
4. `var i = a.length;\r\nwhile(--i)d.push(a[i].id);` - while loop with decrementing index
5. `var z = a.length;\r\nfor(var i=0;i<z;i++)d.push(a[i].id);` - for loop with index-based iteration (using `length`)
6. `for(var i of a)d.push(i.id);` - array method with iterator expression
7. `for(var i=a.length-1;i>=0;i--)d.push(a[i].id);` - for loop with decrementing index from the end

**What's being tested**

Each test case is designed to measure the performance of a different iteration approach when accessing the elements of an array.

**Comparing approaches**

Here's a brief overview of each approach and their pros and cons:

1. **Index-based iteration (`for(var i=0;i<a.length;i++)`)**: This is the most traditional way to iterate over an array in JavaScript. It's straightforward and works well for small arrays.
	* Pros: Easy to understand, no additional libraries required
	* Cons: Can be slow for large arrays due to the overhead of incrementing the index variable
2. **Object property iteration (`for(var i in a)`)**: This approach uses the `in` operator to iterate over the object properties (i.e., array indices). It's often used when iterating over objects with known keys.
	* Pros: Can be faster for large arrays since it doesn't increment an index variable
	* Cons: May not work as expected if the array has non-integer keys or if `in` returns a reserved property name
3. **Array method with callback function (`a.forEach((i)=>d.push(i.id))`)**: This approach uses the `forEach()` method, which is designed for iterating over arrays and performs well since it avoids incrementing an index variable.
	* Pros: Fast, efficient, and widely supported
	* Cons: May not be as straightforward to understand for beginners
4. **While loop with decrementing index (`var i = a.length;\r\nwhile(--i)d.push(a[i].id);`)**: This approach uses a while loop to iterate over the array indices.
	* Pros: Can be faster than traditional loops since it avoids incrementing an index variable
	* Cons: May be less intuitive for beginners and can lead to off-by-one errors if not used carefully
5. **For loop with index-based iteration (`var z = a.length;\r\nfor(var i=0;i<z;i++)d.push(a[i].id);`)**: This approach uses a traditional for loop with an incrementing index variable.
	* Pros: Easy to understand and widely supported
	* Cons: Can be slower than other approaches due to the overhead of incrementing the index variable
6. **Array method with iterator expression (`for(var i of a)d.push(i.id);`)**: This approach uses the array method with an iterator expression.
	* Pros: Fast, efficient, and modern
	* Cons: May not be supported in older browsers or environments
7. **For loop with decrementing index from the end (`for(var i=a.length-1;i>=0;i--)d.push(a[i].id);`)**: This approach uses a for loop with a decrementing index variable, starting from the end of the array.
	* Pros: Can be faster than traditional loops since it avoids incrementing an index variable
	* Cons: May be less intuitive for beginners and can lead to off-by-one errors if not used carefully

**Other considerations**

When choosing an iteration approach, consider the following factors:

* Performance: Which approach is fastest?
* Readability: How easy is the code to understand?
* Maintainability: Can you easily modify or extend the code?
* Compatibility: Is the code supported in older browsers or environments?

In this benchmark, the `forEach()` method with a callback function is likely to be the fastest and most efficient approach. However, the best choice ultimately depends on the specific use case and requirements of your project.

Latest run results:

Run details: (Test run date: 7 years ago)

User agent: Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36

Browser/OS: Chrome 54 on Windows 8.1

View result in a separate tab

Test name	Executions per second
fori	487099.6 Ops/sec
forin	732501.1 Ops/sec
foreach	673884.9 Ops/sec
backwhile	977289.3 Ops/sec
forcachelen	567042.9 Ops/sec
4of	706353.4 Ops/sec
backfor	514949.0 Ops/sec

Related benchmarks:

object keys vs loop (version: 0)

Comparing performance of: fori vs forin vs foreach vs backwhile vs forcachelen vs 4of vs backfor

Created: 7 years ago by: Guest

Jump to the latest result

fori

forin

foreach

backwhile

forcachelen

4of

backfor

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):