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

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();

Historical Performance Data aggregated from 89 community runs

Desktop Results:

Chrome 68 runs

slice()

13.1M/s

charAt()

13.0M/s

character index

13.0M/s

View exact numbers

✓ slice(): 13,118,042 ops/sec
• charAt(): 13,001,692 ops/sec
• character index: 12,994,504 ops/sec

Firefox 21 runs

character index

174.5M/s

charAt()

137.7M/s

slice()

137.7M/s

Fastest: character index (1.3x faster)

View exact numbers

✓ character index: 174,500,560 ops/sec
• charAt(): 137,715,328 ops/sec
• slice(): 137,667,248 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()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 26 days ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/151.0.0.0 Safari/537.36

Browser/OS: Chrome 151 on Linux

View result in a separate tab

character index

111.4M/s

slice()

89.8M/s

charAt()

89.7M/s

View exact numbers

Test name	Executions per second
✓ character index	111,401,816 Ops/sec
slice()	89,765,336 Ops/sec
charAt()	89,713,000 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark and the options being compared.

**What is being tested?**

The benchmark tests three ways to access the first character of a string: using index notation (`str[0]`), `charAt()` method, and slicing with `slice(0, 1)`.

**Options being compared**

Here's a brief overview of each option:

1. **Index notation**: `str[0]`. This is the most straightforward way to access the first character of a string.
2. **`charAt()` method**: `str.charAt(0)`. This method returns the character at a specific index in the string.
3. **Slicing**: `str.slice(0, 1)`. This creates a new string that contains the first character of the original string.

**Pros and Cons of each approach**

* **Index notation (`str[0]`)**:
	+ Pros: Fast, efficient, and widely supported.
	+ Cons: May not be as readable or intuitive for some developers.
* **`charAt()` method**: `str.charAt(0)`.
	+ Pros: More explicit and readable than index notation, especially when accessing characters at specific indices.
	+ Cons: Can be slower due to the overhead of calling a method.
* **Slicing (`str.slice(0, 1)`)**:
	+ Pros: Creates a new string object, which can be useful for certain use cases (e.g., concatenation).
	+ Cons: Slower than index notation and `charAt()`, as it involves creating a new string object.

**Other considerations**

* In modern JavaScript engines, the `charAt()` method is often implemented in native code, making it faster than the other two options. However, this might not be the case for older browsers or specific use cases.
* Slicing can be useful when working with arrays or strings that need to be modified.

**Library usage**

There is no explicit library usage in this benchmark, but `Function.prototype` is used as a no-op function to prevent optimizations from eliminating the loop. This is done to ensure that the benchmark runs consistently across different browsers and engines.

**Special JS features or syntax**

There are no special JavaScript features or syntax used in this benchmark.

Now, let's look at the results:

The results show that slicing (`str.slice(0, 1)`) is the slowest option, followed closely by `charAt()`. Index notation (`str[0]`) is the fastest option. This is expected, as slicing creates a new string object and `charAt()` involves calling a method, which can incur additional overhead.

Keep in mind that these results might not be representative of all browsers or use cases. It's essential to consider specific requirements and constraints when choosing an approach for accessing the first character of a string.

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

Compare methods for testing string's beggining character.

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

Created: 6 years ago by: Guest

Go to the latest result

character index

charAt()

slice()

Historical Performance Data aggregated from 89 community runs

Desktop Results:

Chrome 68 runs

Firefox 21 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() (version: 0) Benchmark.js

Compare methods for testing string's beggining character.

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

Created: 6 years ago by: Guest

Go to the latest result

character index

charAt()

slice()

Historical Performance Data aggregated from 89 community runs

Desktop Results:

Chrome 68 runs

Firefox 21 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()`