Benchmark: For loop vs reduce array change and update

Script Preparation code:

var testArray = [{
test: '123',
arr:[{
  id: 1,
  description: 'Random description.',
  testDate: new Date(),
  testBoolean: true,
  testObject: {
    testString: 'test string',
    testNumber: 12345
  },
  testArray: [{
    myName: 'test name',
    myNumber: 123245
  }]
},{
  id: 2,
  description: 'Random descriptionfdsgdfgd.',
  testNumber: 123456789,
  testBoolean: true,
  testObject: {
    testString: 'test string',
    testNumber: 12345
  },
  testArray: [{
    myName: 'test name',
    myNumber: 123245
  }]
}]
},
{
test: '1234',
arr:[{
  id: 1,
  description: 'Random description.',
  testDate: new Date(),
  testBoolean: true,
  testObject: {
    testString: 'test string',
    testNumber: 12345
  },
  testArray: [{
    myName: 'test name',
    myNumber: 123245
  }]
},{
  id: 2,
  description: 'Random descriptionfdsgdfgd.',
  testNumber: 123456789,
  testBoolean: true,
  testObject: {
    testString: 'test string',
    testNumber: 12345
  },
  testArray: [{
    myName: 'test name',
    myNumber: 123245
  }]
}]
}];

function reduceIt(arr){
 return arr.reduce((acc, val)=>{
   if(val.id == 2){
   	val.description = 'changed it!';
     acc.push(val);
     return acc;
   }
   acc.push(val);
   return acc;
 },[]); 
}

function loopIt(arr){
  var newArray = [];
  for(var x = 0; x < testArray.length; x++){
    if(testArray[x].id == 2){
      testArray[x].description = 'changed it!';
      newArray.push(testArray[x]);
    }
    newArray.push(testArray[x]);
  }
  return newArray;
}

Tests:

For loop
var changeLoop = loopIt(testArray);
Reduce
var changeReduce = reduceIt(testArray);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For loop
Reduce

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

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I'll explain the benchmark and its results in detail.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark test case on MeasureThat.net. The test compares two approaches for modifying an array: a traditional `for` loop and the `reduce()` method. Both methods are used to update the description of specific elements within the array.

**Script Preparation Code**

The script preparation code defines the input data, which is an array of objects with various properties, including `id`, `description`, and `arr`. The array has two elements.

**Functions Under Test**

Two functions are defined:

1. `loopIt(arr)`: This function uses a traditional `for` loop to iterate over the array and update the description of specific elements.
2. `reduceIt(arr)`: This function uses the `reduce()` method to accumulate an updated array with modified elements.

**Benchmark Definition JSON**

The benchmark definition JSON contains two test cases:

1. "For loop": The `loopIt()` function is called, passing the original `testArray`.
2. "Reduce": The `reduceIt()` function is called, passing the original `testArray`.

**Library and Special JS Features**

In this benchmark, the `reduce()` method is used, which is a built-in JavaScript array method. It does not rely on any external libraries.

There are no special JavaScript features or syntax used in this benchmark beyond what's standard for modern JavaScript development.

**Options Compared**

The two options being compared are:

1. **Traditional For Loop**: This approach uses a manual loop to iterate over the array, updating elements as needed.
2. **Reduce Method**: This approach uses the `reduce()` method to accumulate an updated array with modified elements.

**Pros and Cons of Each Approach**

Here's a brief summary of each approach:

* **Traditional For Loop**:
	+ Pros: Can be more readable for complex logic, allows for more control over iteration.
	+ Cons: Typically slower due to the overhead of manual looping.
* **Reduce Method**:
	+ Pros: More concise and expressive, can be faster due to optimized implementation by JavaScript engines.
	+ Cons: May be less readable if not familiar with the method.

**Performance Results**

The latest benchmark results show that the `Reduce` approach is significantly faster than the traditional `For Loop`, executing approximately 4.2 times more iterations per second (5,893,425 vs 1,398,152). This difference is likely due to the optimized implementation of the `reduce()` method by modern JavaScript engines.

**Other Alternatives**

There are other ways to achieve similar results:

* **Using a custom iterator**: You can create a custom iterator object and use it with the `for...of` loop or another array method like `forEach()`.
* **Using a library or framework**: Depending on your specific needs, you might consider using a library like Lodash, which provides a `map()` function that can be used as an alternative to the `reduce()` method.
* **Other array methods**: Other array methods, such as `map()`, `filter()`, and `forEach()`, may also be suitable alternatives depending on your use case.

Related benchmarks:

For loop vs reduce array change and update (version: 0)

for loop vs reduce in new array creation

Comparing performance of: For loop vs Reduce

Created: 7 years ago by: Registered User

Jump to the latest result

For loop

Reduce

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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