Benchmark: String indexOf() === 0 vs. startsWith()

Tests:

Using indexOf()
const str = "some-random-text" const result = str.indexOf("some-random") === 0
Using startsWith()
const str = "some-random-text" const result = str.startsWith("some-random")

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using indexOf()
Using startsWith()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36

Browser/OS: Chrome 100 on Linux

View result in a separate tab

Test name	Executions per second
Using indexOf()	601415872.0 Ops/sec
Using startsWith()	55954884.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what is being tested.

**What is being tested?**

MeasureThat.net is testing two approaches for finding the index of a substring within a string in JavaScript: `indexOf()` and `startsWith()`. The benchmark aims to determine which approach is faster.

**Options compared**

Two options are being compared:

1. **`indexOf()`**: This method returns the index of the first occurrence of a specified value, or -1 if it's not found.
2. **`startsWith()`**: This method returns true if a string starts with another specified value, and false otherwise.

**Pros and cons of each approach**

1. **`indexOf()`**:
	* Pros: Generally faster than `startsWith()`, especially for longer strings, since it only scans the string until it finds the first occurrence of the substring.
	* Cons: Returns the index of the first occurrence, which might not be what you want if there are multiple occurrences. Also, it's slower for shorter strings due to the overhead of searching.
2. **`startsWith()`**:
	* Pros: More intuitive and readable than `indexOf()`, as it directly returns a boolean value indicating whether the string starts with the specified value.
	* Cons: Generally slower than `indexOf()` since it needs to scan the entire string until it finds the first occurrence of the substring.

**Other considerations**

The choice between `indexOf()` and `startsWith()` depends on your specific use case. If you need to find the index of a substring, `indexOf()` is usually sufficient. However, if you want to check if a string starts with a certain value without caring about the rest of the string, `startsWith()` is a better choice.

**Library usage**

There is no library mentioned in this benchmark. The tests are using built-in JavaScript methods: `indexOf()` and `startsWith()`.

**Special JS feature or syntax**

This benchmark does not use any special JavaScript features or syntax that would require knowledge beyond basic JavaScript programming.

**Other alternatives**

If you don't have access to a browser or want to test different implementations, you can write your own microbenchmark in JavaScript using a testing framework like Jest or Mocha. Here's an example:
```javascript
function indexOf(str, substr) {
  for (let i = 0; i < str.length; i++) {
    if (str.startsWith(substr, i)) {
      return i;
    }
  }
  return -1;
}

function startsWith(str, substr) {
  return str.startsWith(substr);
}

const str = 'some-random-text';
const substr = 'some-random';

console.time('indexOf');
for (let i = 0; i < 10000; i++) {
  indexOf(str, substr);
}
console.timeEnd('indexOf');

console.time('startsWith');
for (let i = 0; i < 10000; i++) {
  startsWith(str, substr);
}
console.timeEnd('startsWith');
```
This will give you a similar benchmark to MeasureThat.net's, but running on your local machine instead of a remote browser.

Related benchmarks:

String indexOf() === 0 vs. startsWith() (version: 0)

Which if the two is faster

Comparing performance of: Using indexOf() vs Using startsWith()

Created: 2 years ago by: Registered User

Jump to the latest result

Using indexOf()

Using startsWith()

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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