Benchmark: .startsWith vs .charAt for single character v2

HTML Preparation code:

<div></div>

Script Preparation code:

var data = window.data = [];
const possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var TOTAL_STRINGS = window.TOTAL_STRINGS = 100000;

function getRandomInt(max) {
  return Math.floor(Math.random() * max);
}

function makeRandomString(len) {
  var text = "";
  for( var i=0; i < len; i++ ) {
    text += possible.charAt(getRandomInt(possible.length));
  }
  return text;
}

while (data.length < TOTAL_STRINGS) {
  data.push(makeRandomString(getRandomInt(20)));
}

Tests:

startsWith
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; while (x < TOTAL_STRINGS) { data[x].startsWith("A"); x += 1; }
.charAt
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; while (x < TOTAL_STRINGS) { data[x].charAt(0) === 'A'; x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
.charAt

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.

I'll break down the provided benchmark definition and test cases to explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**

The benchmark measures the performance difference between two approaches:

1. `startsWith` method
2. `.charAt(0) === 'A'` syntax (using a strict equality check)

These two methods are used to check if a string starts with the character 'A'.

**What's being tested?**

The test case is generating 100,000 random strings of varying lengths and checking each one using both `startsWith` and `.charAt(0) === 'A'`. The benchmark measures how many executions per second (ExecutionsPerSecond) are possible for each method.

**Options compared**

1. **`startsWith` method**: This method checks if the string starts with the specified character. It returns a boolean value indicating whether the string begins with the character.
2. **`.charAt(0) === 'A'` syntax**: This syntax uses a strict equality check to compare the first character of the string with 'A'. The `charAt()` method is used to extract the first character, and then the result is compared to 'A' using `===`.

**Pros and Cons**

1. **`startsWith` method**:
	* Pros: Efficient for checking if a string starts with a specific character.
	* Cons: May not be suitable for cases where only a single character needs to be matched (e.g., searching for a specific substring).
2. **`.charAt(0) === 'A'` syntax**:
	* Pros: Can be useful when only a single character is needed, as it extracts the first character and compares it directly.
	* Cons: May be slower due to the additional operation of extracting the first character using `charAt()`.

**Library and purpose**

In this benchmark, there is no specific library being used. However, the `getRandomInt` function is implemented in-house to generate random integers between 0 and a specified maximum value.

**Special JS feature or syntax**

None mentioned in this explanation.

**Other alternatives**

If you wanted to compare other approaches for checking if a string starts with 'A', some alternative methods could include:

1. Using the `indexOf` method: `str.indexOf('A') === 0`
2. Using the `match` method with a regular expression: `/^A/.test(str)`
3. Using a custom implementation, such as iterating through the characters of the string.

Keep in mind that these alternatives might have different performance characteristics compared to the `startsWith` method and the `.charAt(0) === 'A'` syntax used in this benchmark.

Related benchmarks:

.startsWith vs .charAt for single character v2 (version: 0)

Testing some things

Comparing performance of: startsWith vs .charAt

Created: 7 years ago by: Guest

Jump to the latest result

startsWith

.charAt

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):