Benchmark: char index vs charAt() vs slice() vs substr()

Script Preparation code:

var str = 'foo bar baz';
var noop = Function.prototype;

Tests:

character index
if (str[0] == 'f') noop();
charAt()
if (str.charAt(0) == 'f') noop();
slice()
if (str.slice(0, 1) == 'f') noop();
substr()
if (str.substr(0, 1) == 'f') noop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
character index
charAt()
slice()
substr()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Safari/537.36

Browser/OS: Chrome 134 on Linux

View result in a separate tab

Test name	Executions per second
character index	48241808.0 Ops/sec
charAt()	48605420.0 Ops/sec
slice()	40730904.0 Ops/sec
substr()	41635744.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases.

**Benchmark Definition:**
The website is testing four different methods for accessing the first character of a string in JavaScript:

1. `char index` (e.g., `str[0]`)
2. `charAt()` method
3. `slice()` method with a fixed length of 1
4. `substr()` method with a start position of 0 and a length of 1

**Options Compared:**
The benchmark is comparing the performance of these four methods across different browsers and devices.

**Pros and Cons:**

* **char index**: This approach is simple and direct, but it may not be as efficient as other methods since it requires an array index calculation.
* `charAt()`: This method is more explicit and may be faster than the others because it uses a dedicated function call. However, it may incur additional overhead due to the function call.
* `slice()`: This approach creates a new string object with a length of 1, which can lead to memory allocation and deallocation overhead. However, it's also more flexible since it can be used to extract substrings of any length.
* `substr()`: Similar to `slice()`, this method creates a new string object, but it may have slightly better performance due to the fixed start position.

**Library:**
None of the test cases use external libraries, so no additional dependencies need to be considered.

**Special JS Feature/Syntax:**
The benchmark uses the `Function.prototype` object, which is a part of the JavaScript standard library. This allows the code to create a "no-op" function for testing purposes.

**Other Alternatives:**

* For accessing the first character of a string, other approaches like using an arrow function or destructuring could also be used.
* Alternative methods for slicing or substringing strings, such as using `substring()` or a regular expression, are not compared in this benchmark.

In summary, the benchmark is testing the performance of four different methods for accessing the first character of a string in JavaScript. The chosen approach balances simplicity with potential efficiency gains, but the actual performance differences may depend on various factors, including browser and device variations.

Related benchmarks:

char index vs charAt() vs slice() vs substr() (version: 0)

Compare methods for testing string's beggining character.

Comparing performance of: character index vs charAt() vs slice() vs substr()

Created: 4 years ago by: Guest

Jump to the latest result

character index

charAt()

slice()

substr()

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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