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();

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

slice()

13.0M/s

substr()

13.0M/s

character index

13.0M/s

charAt()

13.0M/s

View exact numbers

✓ slice(): 13,005,214 ops/sec
• substr(): 12,989,911 ops/sec
• character index: 12,988,157 ops/sec
• charAt(): 12,969,210 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

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

charAt()

48.6M/s

character index

48.2M/s

substr()

41.6M/s

slice()

40.7M/s

View exact numbers

Test name	Executions per second
✓ charAt()	48,605,420 Ops/sec
character index	48,241,808 Ops/sec
substr()	41,635,744 Ops/sec
slice()	40,730,904 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.

char index vs charAt() vs slice() vs substr() (version: 0) Benchmark.js

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

Go to the latest result

character index

charAt()

slice()

substr()

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

char index vs charAt() vs slice() vs substr() (version: 0) Benchmark.js

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

Go to the latest result

character index

charAt()

slice()

substr()

Historical Performance Data aggregated from 7 community runs

Desktop Results:

Chrome 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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