Benchmark: startsWith vs indexOf benchmark

Script Preparation code:

var string = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.'

Tests:

startsWith
string.startsWith('Lorem')
indexOf
string.indexOf('Lorem')===0

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
indexOf

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the JavaScript microbenchmark on MeasureThat.net.

**Benchmark Overview**

The benchmark compares the performance of two string methods: `startsWith()` and `indexOf()`. The goal is to determine which method is faster for checking if a string starts with a given prefix.

**Test Case Options**

There are two test cases:

1. **`startsWith()`**: This test case measures the time it takes to execute the expression `string.startsWith('Lorem')`.
2. **`indexOf()`**: This test case measures the time it takes to execute the expression `string.indexOf('Lorem')===0`.

**Pros and Cons of Each Approach**

*   **`startsWith()`**:
    *   Pros:
        *   More concise and readable code.
        *   Can be faster since it only needs to check if the prefix is at the beginning of the string, without having to iterate through the entire string.
    *   Cons:
        *   May not work correctly for strings that contain multiple prefixes (e.g., "Hello, World!").
*   **`indexOf()`**:
    *   Pros:
        *   Works correctly for strings with multiple prefixes.
        *   Returns a negative index if the prefix is not found at the beginning of the string.
    *   Cons:
        *   May be slower due to the need to iterate through the entire string until it finds the specified character.

**Library Usage**

There is no explicit library usage mentioned in the benchmark. However, `indexOf()` uses the built-in JavaScript method for searching a string, which relies on various optimizations under the hood (e.g., caching, hash tables).

**Special JS Features or Syntax**

None are explicitly used in this benchmark. The code snippets only utilize standard JavaScript syntax.

**Alternative Approaches**

In addition to `startsWith()` and `indexOf()`, other approaches could be explored:

*   **Regular Expressions**: Use a regular expression with the `test()` method to check if the string starts with the specified prefix.
*   **Substring Extraction**: Create a substring of the original string starting from the beginning, up to but not including the specified prefix.

Here's an example implementation using `RegExp.test()`:
```javascript
var regex = new RegExp('^Lorem', 'i');
console.log(regex.test(string));
```
This approach has similar performance characteristics to `startsWith()`, with a slight overhead due to the creation of a regular expression object.

Related benchmarks:

startsWith vs indexOf benchmark (version: 0)

Comparing performance of: startsWith vs indexOf

Created: 4 years ago by: Guest

Jump to the latest result

startsWith

indexOf

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):