Benchmark: test start with - MeasureThat.net

Script Preparation code:

function startsWith(str, a) {
	return str.substring(0, a.length) === a
}

Tests:

regex
/^user\.view:/.test('user.view:1337'); /^user\.list:/.test('user.view:1337')
startsWith
'user.view:1337'.startsWith('user.view:') 'user.view:1337'.startsWith('user.list:')
custom startsWith
startsWith('user.view:1337', 'user.view:') startsWith('user.view:1337', 'user.list:')
indexOf
'user.view:1337'.indexOf('user.view:') === 0 'user.view:1337'.indexOf('user.list:') === 0
substring
'user.view:1337'.substring(0, 10) === 'user.view:' 'user.view:1337'.substring(0, 10) === 'user.view:'

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
regex
startsWith
custom startsWith
indexOf
substring

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 what's being tested on MeasureThat.net.

**Benchmark Definition JSON**

The benchmark definition represents the code snippet that will be executed to test different JavaScript methods. In this case, there are five benchmark definitions:

1. `startsWith(str, a) { return str.substring(0, a.length) === a; }`
2. `/^user\.view:\/.test('user\.view:1337');`
3. "'user\.view:1337'.startsWith('user\.view:')"
4. "startsWith('user\.view:1337', 'user\.list:'"
5. "'user\.view:1337'.indexOf('user\.view:') === 0"
6. "'user\.view:1337'.substring(0, 10) === 'user\.view:'"

These definitions test different JavaScript methods:

* `startsWith(str, a)` tests the `startsWith` method.
* `/^user\.view:\//.test('user\.view:1337');` and `" user\.view:1337".startsWith('user\.list:')` test regular expression matching (`/regex/`.
* "'user\.view:1337'.indexOf('user\.view:') === 0" tests the `indexOf` method.
* "'user\.view:1337'.substring(0, 10) === 'user\.view:'" tests the `substring` method.

**Options Compared**

The benchmark is comparing different options for each method:

* `startsWith`: using the built-in `startsWith` method vs. implementing a custom version (`startsWith(str, a)`).
* Regular expression matching: using regular expressions to test if a string starts with a certain pattern (`/regex/)`, versus using a simple substring check.
* `indexOf`: testing if an index is 0 compared to a non-existent character (likely for optimization purposes).
* `substring`: testing a specific substring extraction.

**Pros and Cons**

Here are some pros and cons of each approach:

1. **`startsWith(str, a)`**: Pros - more accurate, easy to implement; Cons - may be slower due to the custom implementation.
2. **Regular expression matching (`/regex/)`: Pros - can match complex patterns, easy to read; Cons - may be slower than substring checks.
3. **`indexOf`**: Pros - optimized for specific use cases; Cons - may not work as expected if used with non-existent characters.
4. **`substring`**: Pros - simple and efficient; Cons - may only work with a specific substring.

**Library Usage**

The benchmark uses the `String.prototype.startsWith()` method, which is a built-in JavaScript method. It also uses regular expressions for pattern matching.

**Special JS Features or Syntax**

There are no special JS features or syntax used in this benchmark. The code is standard JavaScript and does not utilize any advanced features like async/await or promises.

**Alternatives**

If you were to implement a custom `startsWith` method, one alternative could be using the `indexOf` method to achieve similar results: `startsWith(str, a) { return str.indexOf(a) === 0; }`. However, this would not be as efficient as the built-in implementation. Another alternative is to use regular expressions for pattern matching, but this may not always be necessary and can add complexity.

Keep in mind that these alternatives are specific to the `startsWith` method only and do not apply to the other benchmark definitions.

Related benchmarks:

test start with (version: 0)

Comparing performance of: regex vs startsWith vs custom startsWith vs indexOf vs substring

Created: 3 years ago by: Guest

Jump to the latest result

regex

startsWith

custom startsWith

indexOf

substring

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):