Benchmark: test-string2 - MeasureThat.net

Tests:

array
String.prototype.replaceAt=function(index, char) { var a = this.split(""); a[index] = char; return a.join(""); } 'abcde'.replaceAt(2,'a')
obj.assign
String.prototype.replaceAt = function(index, char) { return Object.assign([...this], {[index]: char}).join(``); }; 'abcde'.replaceAt(2,'a')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
array
obj.assign

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36

Browser/OS: Chrome 90 on Windows

View result in a separate tab

Test name	Executions per second
array	1907114.1 Ops/sec
obj.assign	648385.3 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in the provided JSON benchmark.

**Benchmark Definition**

The benchmark definition is essentially a script that defines a function to be measured. There are two variations of this function:

1. `String.prototype.replaceAt` with `Array.prototype.join`:
```javascript
String.prototype.replaceAt = function(index, char) {
    var a = this.split("");
    a[index] = char;
    return a.join("");
};
'abcde'.replaceAt(2,'a');
```
This implementation creates a new array by splitting the string into individual characters using `Array.prototype.split("")`. It then modifies the character at the specified index (`index`) to be the provided character (`char`). Finally, it joins the modified array back into a single string using `Array.prototype.join("")`.

2. `String.prototype.replaceAt` with `Object.assign` and `[...this]`:
```javascript
String.prototype.replaceAt = function(index, char) {
    return Object.assign([...this], {[index]: char}).join("");
};
'abcde'.replaceAt(2,'a');
```
This implementation uses the spread operator (`[...this]`) to create a new array containing all characters of the original string. It then uses `Object.assign()` to merge this array with an object that contains only the character at the specified index (`index`), which is set to be the provided character (`char`). The resulting object is then joined back into a single string using `Array.prototype.join("")`.

**Comparison**

The two implementations are being compared in terms of performance.

**Pros and Cons**

1. **Array implementation**
	* Pros:
		+ Simple and easy to understand.
		+ Uses built-in array methods that are well-optimized by the browser engine.
	* Cons:
		+ Creates an unnecessary intermediate array, which can lead to memory allocation overhead.
2. **Object implementation with `Object.assign()`**
	* Pros:
		+ Avoids the creation of an intermediate array, reducing memory allocation overhead.
	* Cons:
		+ May have slower performance due to the additional overhead of creating and merging objects.

**Library**

In both test cases, no external libraries are used. The implementation relies solely on built-in JavaScript methods and syntax.

**Special JS Feature or Syntax**

There is no special JavaScript feature or syntax being tested in this benchmark. Both implementations use standard JavaScript features like array methods (`Array.prototype.split()`, `Array.prototype.join()`) and object methods (`Object.assign()`).

**Alternatives**

If you were to rewrite these benchmarks, here are some alternative approaches:

* For the Array implementation:
	+ Use a library like Lodash to create an optimized string manipulation function.
	+ Implement the string replacement using a simple loop instead of relying on built-in array methods.
* For the Object implementation with `Object.assign()`:
	+ Use a library like Immutable.js to create an immutable data structure for better performance and code readability.
	+ Implement the string replacement using a more specialized library like FastString or String manipulation libraries specific to your use case.

Keep in mind that these alternatives would likely have different performance characteristics and may not be suitable for all use cases.

Related benchmarks:

test-string2 (version: 0)

Comparing performance of: array vs obj.assign

Created: 4 years ago by: Registered User

Jump to the latest result

array

obj.assign

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):