Benchmark: Repeating String

Tests:

Simple for loop
function repeatify(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } let result = ''; for (let i = 0; i < repetitions; i++) { result += string; } return result; } repeatify('*', 10000);
Extended for loop
function repeatify2(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } const isEven = repetitions % 2 === 0; const iterations = Math.floor(repetitions / 2); const stringTwice = string + string; let result = ''; for (let i = 0; i < iterations; i++) { result += stringTwice; } if (!isEven) { result += string; } return result; } repeatify2('*', 10000);
Log based
function repeatify3(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } const cache = new Map(); function repeat(string, repetitions) { if (repetitions === 0) { return ''; } const log = Math.floor(Math.log2(repetitions)); let result; if (cache.has(log)) { result = cache.get(log); } else { result = string; for (let i = 1; i <= log; i++) { result += result; cache.set(i, result); } } const repetitionsProcessed = Math.pow(2, log); const repetitionsLeft = repetitions - repetitionsProcessed; return result + repeat(string, repetitionsLeft); } return repeat(string, repetitions); } repeatify3('*', 10000);
Array join
function repeatify4(string, repetitions) { if (repetitions < 0 || repetitions === Infinity) { throw new RangeError('Invalid repetitions number'); } var resultArray = new Array(repetitions); for (let i = 0; i < repetitions; i++) { resultArray[i] = string; } return resultArray.join(''); } repeatify4('*', 10000);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Simple for loop
Extended for loop
Log based
Array join

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:139.0) Gecko/20100101 Firefox/139.0

Browser/OS: Firefox 139 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Simple for loop	47869.8 Ops/sec
Extended for loop	54770.8 Ops/sec
Log based	2675591.8 Ops/sec
Array join	32677.6 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring the performance of different string repetition approaches is crucial in understanding how JavaScript engines handle such tasks.

**Benchmark Test Cases**

The test cases provided measure the execution speed of four different string repetition functions:

1. **Simple for loop**: The function `repeatify(string, repetitions)` uses a traditional for loop to repeat the string.
2. **Extended for loop**: The function `repeatify2(string, repetitions)` uses an extended for loop with an additional check to append the original string when the number of repetitions is odd.
3. **Log based**: The function `repeatify3(string, repetitions)` uses a logarithmic approach to cache and reuse previously computed results, reducing the number of iterations required.
4. **Array join**: The function `repeatify4(string, repetitions)` creates an array with repeated strings using the `join()` method.

**Options Compared**

The test cases compare the performance of these four approaches under different conditions:

* Repetitions: 10000
* String length: varies (not explicitly stated, but can be inferred from the provided implementations)
* Browser and device information: Chrome 55 on a Macintosh with Intel Mac OS X 10_11_6

**Pros and Cons of Each Approach**

1. **Simple for loop**: Efficient, easy to understand, and suitable for small repetitions. However, it may not perform well for large repetitions due to the overhead of the loop.
	* Pros: Simple, easy to implement
	* Cons: May be slow for large repetitions
2. **Extended for loop**: Similar to the simple for loop but with an additional check to append the original string when necessary. This approach is slightly more efficient than the simple loop.
	* Pros: Slightly faster than simple for loop, handles odd repetition cases
	* Cons: May be slower than log-based approach for very large repetitions
3. **Log based**: Uses a logarithmic approach to cache and reuse previously computed results, reducing the number of iterations required.
	* Pros: Can handle very large repetitions efficiently, reduces overhead
	* Cons: More complex implementation, may require additional memory for caching
4. **Array join**: Creates an array with repeated strings using the `join()` method.
	* Pros: Easy to implement, efficient for small repetitions
	* Cons: May be slower than other approaches for large repetitions due to array creation and concatenation overhead

**Other Considerations**

When choosing a string repetition approach, consider the following factors:

* Repetition size: For very large repetitions, log-based or array join approaches may be more efficient.
* String length: Shorter strings can be repeated faster than longer strings.
* Performance: If speed is critical, log-based or array join approaches might be better choices.

**Alternatives**

Other alternatives for string repetition could include:

* Using a library like `repeat-string` or `string-repeat`, which provide optimized implementations for different use cases.
* Implementing a custom repeat function using techniques like dynamic programming or memoization.
* Utilizing JavaScript's built-in methods, such as `String.prototype.repeat()` (available in modern browsers).

Keep in mind that the choice of approach depends on specific requirements and performance constraints.

Related benchmarks:

Repeating String (version: 0)

Comparing performance of: Simple for loop vs Extended for loop vs Log based vs Array join

Created: 9 years ago by: Guest

Jump to the latest result

Simple for loop

Extended for loop

Log based

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):