Benchmark: Array join vs string concat

Script Preparation code:

var arr = [];
var str = '';
var i = 0;
var start = 0;
var limit = 1000000;

Tests:

Array join
for(i = start; i < limit; i++) { arr[i] = "string"; } arr.join("");
String concat
for(i = start; i < limit; i++) { str += "string"; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array join
String concat

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):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what is being tested.

**Benchmark Definition**

The benchmark is comparing two approaches: Array `join()` method and string concatenation using the `+` operator (`str += "string"`).

**Script Preparation Code**

This section sets up variables:
- `arr`: an empty array
- `str`: an empty string
- `i`: a counter variable initialized to 0
- `start`: a threshold value (1000000) that marks the beginning of the benchmarking range
- `limit`: another threshold value that defines the end of the benchmarking range

**Html Preparation Code**

This section is not applicable, as it's commented out.

Now, let's analyze the individual test cases:

1. **Array join**
   ```javascript
for(i = start; i < limit; i++) {
    arr[i] = "string";
}
arr.join("");
```
   In this case, we're filling the array `arr` with the string `"string"` using a for loop and then calling the `join()` method on it to concatenate all elements in the array into a single string.

2. **String concat**
   ```javascript
for(i = start; i < limit; i++) {
    str += "string";
}
```
   Here, we're building up a large string `str` by concatenating `"string"` repeatedly using the `+` operator (`+=`).

**Comparison and Pros/Cons**

We are comparing the performance of two methods:

- **Array join:** Using the `join()` method is generally faster than string concatenation. This is because it avoids creating temporary strings in the process of adding elements to the resulting string, thus reducing overhead.

- **String concat:** String concatenation using `+=` operator can be slower due to intermediate string creation during each iteration of the loop. However, modern JavaScript engines often optimize this operation by reusing existing buffers for string construction and combining them into a single final output, which minimizes overall performance impact.

**Library/Module Usage**

- None of these test cases utilize any external library or module directly in their code.

**Special JS Feature/Syntax**

There's no special JavaScript feature or syntax used in the provided benchmarking scripts.

Related benchmarks:

Array join vs string concat (version: 0)

Comparing performance of: Array join vs String concat

Created: 4 years ago by: Guest

Jump to the latest result

Array join

String concat

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):