Benchmark: array / object iteration

Script Preparation code:


var arr = [];
var obj = {};
var i=1000000;
while(i--){
  arr.push(i);
  obj[i]=i;
}

Tests:

array iterate
for(var i=0; i<arr.length; i++){ var test = arr[i]; test = null; }
object iteration
for(var p in obj){ var test = obj[p]; test = null; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array iterate
object iteration

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/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Linux

View result in a separate tab

Test name	Executions per second
array iterate	503.4 Ops/sec
object iteration	12.6 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested, compared, and considered.

**Benchmark Definition**
The provided JSON represents a JavaScript microbenchmark that tests two different approaches to iterate over arrays and objects:

1. `array / object iteration`
2. `for(var i=0; i<arr.length; i++){\r\n  var test = arr[i];\r\n  test = null;\r\n}`
3. `for(var p in obj){\r\n  var test = obj[p];\r\n  test = null;\r\n}`

The first option, `array / object iteration`, is not explicitly defined, but it's implied that it should be the same as the second and third options.

**Options Compared**

The benchmark compares the performance of three approaches to iterate over arrays and objects:

1. **Direct indexing**: `for(var i=0; i<arr.length; i++){\r\n  var test = arr[i];\r\n  test = null;\r\n}` This approach uses direct indexing to access elements in the array.
2. **For-in loop**: `for(var p in obj){\r\n  var test = obj[p];\r\n  test = null;\r\n}` This approach uses a for-in loop to iterate over the object's properties.

**Pros and Cons**

1. **Direct indexing**:
	* Pros: Fast, as it avoids the overhead of property lookup.
	* Cons: May not work correctly if the array is sparse or has non-contiguous index values.
2. **For-in loop**:
	* Pros: Works with both arrays and objects, and can handle sparse arrays and non-contiguous index values.
	* Cons: Slower than direct indexing due to property lookup.

**Library Usage**
In this benchmark, no libraries are used explicitly. However, it's worth noting that some JavaScript engines may use internal libraries or optimizations that might affect the results of this benchmark.

**Special JS Features**
None are mentioned in this benchmark. The test cases only use standard JavaScript syntax and features.

**Alternative Approaches**

Other approaches to iterate over arrays and objects could include:

1. **forEach()**: A modern approach that uses a callback function to iterate over an array or object.
2. **Map()**: Another modern approach that uses a map function to create a new array with transformed values from the original array.
3. **Loops with conditional statements**: Alternative loop structures, such as `while` loops with conditional statements, might also be used for iteration.

It's worth noting that MeasureThat.net provides a wide range of benchmarks and test cases for various JavaScript features and libraries. If you're interested in exploring more benchmarking options or specific libraries, the MeasureThat.net website offers an extensive collection of resources.

Related benchmarks:

array / object iteration (version: 0)

Comparing performance of: array iterate vs object iteration

Created: 7 years ago by: Guest

Jump to the latest result

array iterate

object iteration

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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