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:

No previous run results

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Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

LLMs can make mistakes. Check important info.

This benchmark compares two ways to check if a string starts with the letter "A":

**Method 1: `startsWith()`**

* **Benchmark Definition:**  `data[x].startsWith("A");` 
* This method directly checks if the string at index `x` in the `data` array starts with the letter "A".

**Method 2: `.charAt(0) == 'A'`**

* **Benchmark Definition:** `data[x].charAt(0) == 'A';` 
* This method first retrieves the character at index 0 of the string using `charAt(0)`, and then compares it to the letter "A".

**Pros and Cons:**

* **`startsWith()` (Method 1):** 
    * **Pros:** More concise, potentially more performant as it's designed specifically for this task. Modern JavaScript engines are likely optimized for `startsWith()`.
    * **Cons:**  Introduced in ES6, so not supported in older browsers.

* **`.charAt(0) == 'A'` (Method 2):**
    * **Pros:** Works in all browsers due to its older nature.
    * **Cons:** Less concise and potentially less performant because it involves an extra step of retrieving a character.

**Other Considerations:**

* **Data Size:** The benchmark tests on a large dataset (100,000 strings), making performance differences more noticeable. 
* **String Length:**  The strings are randomly generated with lengths up to 20 characters, which influences the impact of each method. 
* **Profiling:** To get a definitive answer on performance, detailed profiling tools should be used in addition to benchmark results.

**Alternatives:**

While not directly explored here, other string comparison techniques exist:

* **Regular Expressions:**  You could use a regular expression like `/^A/` to check for the "A" at the beginning of a string. 
* **Manual Comparison:** A very basic approach would be to compare the first character of the string with "A".

**Note:** This benchmark focuses on raw performance. In real-world applications, code readability and maintainability often outweigh minor performance differences.

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 gemma2:9b, generated one year ago):