Benchmark: String.charAt vs String.sub

Script Preparation code:

str = ''
let i = 10 ** 3
while (--i) str = str + i

Tests:

String.charAt
for (let i = 0, l = str.length; i < l; i++) str.charAt(i)
String.sub
for (let i = 0, l = str.length; i < l; i++) str[i]

Historical Performance Data aggregated from 6 community runs

Desktop Results:

Chrome 6 runs

String.sub

253K/s

String.charAt

251K/s

View exact numbers

✓ String.sub: 252,844 ops/sec
• String.charAt: 251,443 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
String.charAt
String.sub

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/146.0.0.0 Safari/537.36

Browser/OS: Chrome 146 on Windows

View result in a separate tab

String.charAt

342K/s

String.sub

326K/s

View exact numbers

Test name	Executions per second
✓ String.charAt	342,070 Ops/sec
String.sub	325,698 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.

**Benchmark Definition**

The benchmark is comparing two approaches for accessing the last character of a string in JavaScript: `String.charAt(i)` and `str[i]`. The benchmark aims to measure which approach is faster.

**Options Compared**

There are two options being compared:

1. **`String.charAt(i)`**: This method uses the `charAt()` function to get the character at the specified index.
2. **`str[i]`**: This is a direct property access, indexing into the string using the array-like notation (`str[i]`).

**Pros and Cons**

**`String.charAt(i)`**:

* Pros:
	+ More readable and self-documenting code
	+ Less prone to errors due to explicit index specification
* Cons:
	+ May be slower due to the overhead of calling a function

**`str[i]`**:

* Pros:
	+ Faster, as it avoids the function call overhead
	+ Can be more concise in certain situations
* Cons:
	+ Less readable and maintainable code (less explicit about what's happening)
	+ More prone to errors due to indexing mistakes

**Other Considerations**

In general, when working with strings in JavaScript, `String.charAt(i)` is a safer choice because it provides more explicit control over the indexing process. However, for performance-critical applications or situations where every cycle counts, using direct property access (`str[i]`) might be a better option.

**Library and Special JS Feature**

There are no external libraries used in this benchmark, nor any special JavaScript features (like ES6+ syntax or dynamic imports) that would affect the comparison. The focus is solely on the two string manipulation approaches.

**Alternative Approaches**

Other possible ways to access the last character of a string could include:

1. `str.length - 1` ( direct indexing with subtraction)
2. Using `String.prototype.slice()` and accessing the last element (`str.slice(-1)`)
3. Creating a new string by taking a substring from the end of the original string (`str.substring(str.length-1)`)

These alternatives would likely incur additional overhead compared to using `str[i]`, but could provide different trade-offs in terms of readability and maintainability.

Keep in mind that this benchmark focuses on comparing two specific approaches, rather than exploring all possible ways to achieve a similar result.

String.charAt vs String.sub (version: 0)

Comparing performance of: `String.charAt vs String.sub`

Created: 3 years ago by: Guest

Go to the latest result

String.charAt

String.sub

Historical Performance Data aggregated from 6 community runs

Desktop Results:

Chrome 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

String.charAt vs String.sub (version: 0)

Comparing performance of: String.charAt vs String.sub

Created: 3 years ago by: Guest

Go to the latest result

String.charAt

String.sub

Historical Performance Data aggregated from 6 community runs

Desktop Results:

Chrome 6 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `String.charAt vs String.sub`