Benchmark: .startsWith vs .charAt for single character v3

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:

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Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

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Let's break down the benchmark test.

**What is being tested?**

The test compares two different ways to check if a string starts with a specific character: `startsWith` and `charAt`.

Specifically, the test creates an array of 100,000 random strings (each up to 20 characters long) and then repeatedly checks each string to see if it starts with either "A" or "B". The two test cases use different methods to perform this check:

1. **startsWith**: This method is called on each string in the array, passing in the character "A" as an argument.
2. **charAt**: This method is called on each string in the array, and its first character is compared with "A" using a loose equality (`==`) operator.

**What options are being compared?**

The two test cases compare:

* **startsWith vs charAt**: The primary comparison is between using `startsWith` (a more modern JavaScript method) versus using `charAt` followed by a loose equality check.

**Pros and cons of the approaches:**

1. **startsWith**:
	* Pros: More concise and easier to read, as it directly checks if a string starts with a specific prefix.
	* Cons: May be slower than manual iteration (e.g., using `charAt`) for very large strings or in performance-critical code.
2. **charAt**:
	* Pros: Allows for more control over the check (e.g., using strict equality `===`), and may be faster for very large strings.
	* Cons: Requires manual iteration, which can make the code less readable and more error-prone.

**Other considerations:**

1. **String length**: The test creates random strings up to 20 characters long. If the strings were longer or shorter, the performance difference between `startsWith` and `charAt` might be more pronounced.
2. **Character set**: The test uses only ASCII letters (A-Z, a-z) as potential prefixes. If other characters or Unicode code points were used, the results might differ.

**Library usage:**

None in this test case.

**Special JavaScript features or syntax:**

1. **startsWith**: This is a built-in method on the String prototype, introduced in ECMAScript 2015 (ES6). It takes a string prefix as an argument and returns `true` if the original string starts with that prefix.
2. **charAt**: This is also a built-in method on the String prototype, which returns the character at the specified index.

**Alternatives:**

1. **IndexOf**: Another method on the String prototype that can be used to check if a string contains a specific substring (including prefixes). While not directly comparable to `startsWith` or `charAt`, it's worth considering for other use cases.
2. **Manual iteration**: You could write custom code using loops and conditional statements to manually iterate over each character in the string, similar to what's done with `charAt`. However, this approach is generally less readable and more error-prone than using built-in methods like `startsWith`.

Related benchmarks:

.startsWith vs .charAt for single character v3 (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 llama3.1:latest, generated one year ago):