Benchmark: String.prototype.concat vs Array.prototype.join

Script Preparation code:



var sArr = [];

Tests:

String concatentation
let str = ""; for (let i = 1000; i > 0; i--) { str += "String concatenation. "; }
Array join (using indexes)
const sArr = []; for (let i = 1000; i > 0; i--) { sArr[i] = "String concatenation. "; } const str = sArr.join("");
Array join (using push)
const sArr = []; for (let i = 1000; i > 0; i--) { sArr.push("String concatenation. "); } const str = sArr.join("");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
String concatentation
Array join (using indexes)
Array join (using push)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Linux

View result in a separate tab

Test name	Executions per second
String concatentation	308604.8 Ops/sec
Array join (using indexes)	69452.6 Ops/sec
Array join (using push)	70926.4 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript benchmark test case on the MeasureThat.net website. The test compares three different approaches to concatenate strings:

1. `String.prototype.concat()`: This method concatenates two or more strings together, returning the resulting string.

2. `Array.prototype.join()` with indexes: This method takes an array of strings and joins them together with a specified separator.

3. `Array.prototype.push()` followed by `join()`: This approach involves pushing each string to be concatenated onto an array, which is then joined using the `join()` method.

Let's examine each option in detail:

**Option 1: String.prototype.concat()**

Pros:
- Native JavaScript support.
- Simple and concise syntax.

Cons:
- Can lead to a lot of temporary objects being created if done in a loop.
- Can be slower than other methods for large datasets due to string concatenation internally.

In this test case, the first benchmark measures the performance of `String.prototype.concat()`.

**Option 2: Array.join() with indexes**

Pros:
- More efficient than concatenating strings using `+` operator because it avoids creating temporary strings.
- Can be faster for large datasets as it uses a more optimized algorithm.

Cons:
- Less intuitive syntax, especially if the developer is not familiar with this method.
- The array needs to be initialized beforehand and can lead to performance issues if too big.

In this test case, the second benchmark measures the performance of using indexes to join an array of strings with `Array.prototype.join()`.

**Option 3: Array.push() followed by join()**

Pros:
- Less memory-intensive than using arrays of characters for large numbers of concatenations because it uses push and then join.
- More efficient in terms of time as well, as the algorithm doesn't need to create temp objects.

Cons:
- The syntax is more complex compared to other methods like `+` or `concat`.
- May have performance overhead due to array resizing during pushes.

In this test case, the third benchmark measures the performance of using `Array.prototype.push()` followed by `join()`.

**Library and purpose**

There's no library mentioned in the provided JSON. However, some notable libraries for string manipulation in JavaScript include:

* Lodash: Provides various utility functions like `string.join()` which can be used instead of `Array.prototype.join()`.
* String-Parse: A regex-based implementation of strings that is useful when you want precise control over parsing.

**Special JS feature or syntax**

There's no special JS feature or syntax mentioned in the provided JSON. However, some notable features include:

* Let and const declarations (used in the benchmark definitions).
* Template literals (used to create string literals like `let str = \"\";`).

The test results show that `Array.prototype.join()` with indexes provides the best performance among all three options, followed closely by `push()` followed by `join()`, and then `String.prototype.concat()`. These results suggest that for large datasets, using a more efficient algorithm is crucial, which is why methods like `+` operator or optimized algorithms for string concatenation can be preferred.

Related benchmarks:

String.prototype.concat vs Array.prototype.join (version: 0)

Comparing performance of: String concatentation vs Array join (using indexes) vs Array join (using push)

Created: 4 years ago by: Registered User

Jump to the latest result

String concatentation

Array join (using indexes)

Array join (using push)

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):