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();

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

Autogenerated LLM Summary (model llama3.2:3b, generated one month 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.

Latest run results:

Run details: (Test run date: 13 minutes ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:132.0) Gecko/20100101 Firefox/132.0

Browser/OS: Firefox 132 on Windows

View result in a separate tab

Test name	Executions per second
character index	134350624.0 Ops/sec
charAt()	126342976.0 Ops/sec
slice()	126802360.0 Ops/sec

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Created: 4 years ago by: Guest

Jump to the latest result

character index

charAt()

slice()

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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