Benchmark: String.concat vs array.join

Script Preparation code:

var str = "";
var i;
var sArr = [];

Tests:

String concatentation
for (i = 1000; i > 0; i--) { sArr[i] = "String concatenation. "; } str = ''.concat(...sArr);
Array join
for (i = 1000; i > 0; i--) { sArr[i] = "String concatenation. "; } str = sArr.join("");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
String concatentation
Array join

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36

Browser/OS: Chrome 141 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
String concatentation	53769.2 Ops/sec
Array join	48846.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided benchmark tests two different approaches to concatenate strings in JavaScript: using the `concat` method and using the `join` method on an array.

**Options compared**

There are two main options being compared:

1. **String Concatenation**: Using the `+` operator or the `concat` method to concatenate multiple strings.
2. **Array Join**: Using the `join` method on an array of strings to concatenate them.

**Pros and Cons of each approach:**

* **String Concatenation**:
	+ Pros:
		- Simple and easy to understand
		- No additional data structure needed (array)
	+ Cons:
		- Can be slower for large numbers of concatenations due to string creation overhead
		- Creates a new string object on each concatenation, leading to potential memory issues
* **Array Join**:
	+ Pros:
		- Can be faster for large numbers of concatenations since it avoids creating multiple strings
		- More efficient use of memory, as only one string is created
	+ Cons:
		- Requires an array of strings, which can be more verbose to create
		- May not be as clear or intuitive for developers who are unfamiliar with the `join` method

**Library and its purpose**

The `concat` method is a built-in JavaScript function that concatenates one or more arguments into a single string. It's used extensively in web development for string manipulation.

**Special JS feature or syntax**

There is no special JS feature or syntax mentioned in this benchmark. The focus is solely on comparing two common string concatenation approaches.

**Other alternatives**

In addition to the `concat` method and array join, there are a few other ways to concatenate strings in JavaScript:

* **Template literals**: Introduced in ECMAScript 2015 (ES6), template literals allow you to embed expressions inside string literals using backticks (`). For example: `const str = `${expression1} ${expression2}`;`.
* **String spread operator**: Also introduced in ES6, the spread operator (`...`) can be used to concatenate strings. For example: `const str = [...expression1, ..., expression2];`.

While these alternatives are not mentioned in this benchmark, they provide additional options for string concatenation and manipulation in JavaScript.

**Benchmark preparation code**

The script preparation code provided:
```javascript
var str = "";
var i;
var sArr = [];
```
Sets up an empty string `str` and an empty array `sArr`. This is likely done to create a clean slate for testing, allowing the benchmark to focus on the concatenation methods being compared.

**Individual test cases**

The two test cases are identical, with only the `Benchmark Definition` code varying between them. The main difference lies in how the strings are concatenated: using the `concat` method or the `join` method on an array of strings.

In summary, this benchmark tests the performance and efficiency of two common string concatenation approaches in JavaScript: using the `+` operator or the `concat` method versus using the `join` method on an array of strings.

Related benchmarks:

String.concat vs array.join (version: 0)

Comparing performance of: String concatentation vs Array join

Created: one year ago by: Guest

Jump to the latest result

String concatentation

Array join

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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