Benchmark: .startsWith vs .charAt vs str[0] for single character

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
.charAt
str[0]

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 the benchmark and analyze what's being tested, the options compared, pros and cons of each approach, and other considerations.

**Benchmark Overview**

The benchmark measures the performance of three different ways to check if a single character is "A" at the beginning of a string:

1. `str.startsWith("A")`
2. `str.charAt(0) === 'A'`
3. `str[0] === 'A'`

These checks are performed on a large dataset of 100,000 random strings generated from a set of possible characters.

**Options Compared**

The benchmark compares the performance of three options:

1. `str.startsWith("A")`: This method checks if the string starts with "A" by using the `startsWith` method.
2. `str.charAt(0) === 'A'`: This method extracts the first character of the string and checks if it's equal to "A".
3. `str[0] === 'A'`: This method also extracts the first character of the string and checks if it's equal to "A", but using array indexing instead of a function call.

**Pros and Cons**

1. **`str.startsWith("A")`**:
	* Pros: Simple, concise, and efficient.
	* Cons: May be slower than other methods due to the overhead of the `startsWith` method.
2. **`str.charAt(0) === 'A'`**:
	* Pros: Allows for more flexibility in checking multiple characters at once.
	* Cons: Requires an extra function call, which may introduce overhead.
3. **`str[0] === 'A'`**:
	* Pros: Similar to `charAt`, but using array indexing instead of a function call.
	* Cons: May be slightly slower than `charAt` due to the overhead of array indexing.

**Other Considerations**

* The benchmark uses a large dataset to ensure that any performance differences between the options are representative.
* The test is run on Chrome Mobile 99, which may introduce platform-specific factors that affect performance.
* The use of `window.data`, `window.TOTAL_STRINGS`, and other globals suggests that this benchmark is intended for testing in a browser environment.

**Library and Special JS Features**

No libraries or special JavaScript features are used beyond the standard DOM and global variables.

**Alternatives**

Other alternatives to these options might include:

* Using a regular expression (`^A`) instead of `startsWith`
* Using a custom implementation that avoids function calls and array indexing
* Testing other string comparison methods, such as using `slice(1)` or `substring(1)`

However, the current benchmark provides a clear and concise way to compare the performance of these three options in a controlled environment.

Related benchmarks:

.startsWith vs .charAt vs str[0] for single character (version: 0)

Testing some things

Comparing performance of: startsWith vs .charAt vs str[0]

Created: 4 years ago by: Guest

Jump to the latest result

startsWith

.charAt

str[0]

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):