Benchmark: Str concat vs Array join to put strings together

HTML Preparation code:

<!--your preparation HTML code goes here-->

Tests:

Str concat
let str = ''; for (let i = 0; i < 1000; i += 1) { str += Math.floor(Math.random() * Date.now()).toString(36); } console.log(str);
Array join
let str = []; for (let i = 0; i < 1000; i += 1) { str.push(Math.floor(Math.random() * Date.now()).toString(36)); } console.log(str.join(''));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Str concat
Array join

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 months 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

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Test name	Executions per second
Str concat	4305.2 Ops/sec
Array join	6020.4 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 7 months ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON tests the performance of two different string concatenation methods in JavaScript: direct string concatenation using the `+=` operator and joining an array using the `Array.join()` method. Here's a breakdown of the benchmark:

### Options Compared

1. **String Concatenation (`Str concat`)**:
   - **Benchmark Definition**: The code initializes an empty string `str` and iteratively adds random strings to it using the `+=` operator.
   - **Execution**: 
     ```javascript
     let str = '';
     for (let i = 0; i < 1000; i += 1) {
       str += Math.floor(Math.random() * Date.now()).toString(36);
     }
     console.log(str);
     ```

2. **Array Join (`Array join`)**:
   - **Benchmark Definition**: This option initializes an empty array `str` and pushes random strings into it. After the loop, it joins the elements of the array into a single string.
   - **Execution**:
     ```javascript
     let str = [];
     for (let i = 0; i < 1000; i += 1) {
       str.push(Math.floor(Math.random() * Date.now()).toString(36));
     }
     console.log(str.join(''));
     ```

### Performance Results

Based on the latest benchmark results, the `Array join` method performs better, achieving approximately **6020.44 executions per second** compared to the **4305.18 executions per second** for `Str concat`. This indicates a noticeable performance advantage for the array joining approach in this specific scenario.

### Pros and Cons

#### String Concatenation (`Str concat`):
- **Pros**:
  - Simplicity: The syntax is straightforward and easy to understand.
  - Less code overhead: Directly concatenating strings may appear cleaner for smaller scales.

- **Cons**:
  - Performance degradation: Using `+=` repeatedly creates new strings with each concatenation, leading to higher memory overhead and slower execution as the string grows in size.

#### Array Join (`Array join`):
- **Pros**:
  - Improved performance: Especially beneficial for concatenating many strings, as it minimizes memory allocation compared to repeated mutations of the string.
  - More optimal for larger datasets: Uses an array to gather parts and joins them at once, which is more efficient.

- **Cons**:
  - Additional complexity: Slightly more complex to implement compared to simple string concatenation.

### Other Considerations and Alternatives

1. **Template Literals**: One option not tested here is the use of ES6 template literals. Although it provides a readable way to concatenate strings, in terms of performance, using an array join or simple concatenation may yield better results depending on the context and volume of strings.

2. **StringBuilder**: In languages that support it (like Java), a StringBuilder often provides better performance for constructing strings. In JavaScript, sticking to arrays with joins is the closest approach.

3. **Reduce and Map Functions**: Alternatives using functional programming (like `Array.reduce()`) can also concatenate strings but may not be as performant as the array join method tested here.

### Conclusion

The benchmark effectively illustrates the performance differences between two common methods for string concatenation. Opting for the `Array.join()` method is generally recommended for scenarios involving multiple string concatenations, especially when performance is a critical factor, as demonstrated by the results obtained in this benchmark.

Related benchmarks:

Str concat vs Array join to put strings together (version: 1)

Comparing performance of: Str concat vs Array join

Created: 7 months ago by: Guest

Jump to the latest result

Str concat

Array join

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 7 months ago):