Benchmark: Last char in a string: char index vs charAt() vs slice() vs at()

Script Preparation code:

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

Tests:

character index
if (str[str.length-1] == 'z') noop();
charAt()
if (str.charAt(str.length-1) == 'z') noop();
slice()
if (str.slice(-1) == 'z') noop();
at()
if (str.at(-1) == 'z') noop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

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/114.0.0.0 Safari/537.36

Browser/OS: Chrome 114 on Linux

View result in a separate tab

Test name	Executions per second
character index	5219980.0 Ops/sec
charAt()	5352677.5 Ops/sec
slice()	7764398.5 Ops/sec
at()	7209826.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared options, their pros and cons, library usage, special JS features, and alternatives.

**Benchmark Overview**

The provided benchmark compares four methods to access the last character of a string: `char index`, `charAt()`, `slice()`, and `at()`.

**Methods Compared**

1. **Char Index**: Directly accessing the last character of the string using indexing (`str[str.length-1]`).
2. **charAt()**: Using the `charAt()` method, which returns the character at a specified index.
3. **Slice()**: Using the `slice()` method to get a substring starting from the end of the original string.
4. **at()**: A relatively new addition to JavaScript, introduced in ECMAScript 2020, which allows accessing elements by their key (in this case, the last character) using the `at()` method.

**Pros and Cons**

1. **Char Index**:
	* Pros: Simple, efficient, and well-supported.
	* Cons: Can lead to performance issues if the string is very large.
2. **charAt()**:
	* Pros: Wide support and good performance.
	* Cons: Requires a separate method call, which can be slower than direct indexing.
3. **Slice()**:
	* Pros: Allows getting a substring without having to calculate its length.
	* Cons: Can lead to unnecessary string creation and copies if not used correctly.
4. **at()**:
	* Pros: Provides an elegant way to access elements by their key, especially useful for objects with large numbers of keys.
	* Cons: Still relatively new and may not be supported in older browsers or environments.

**Library Usage**

None explicitly mentioned; however, the `noop` function used as a placeholder is part of the JavaScript language itself (`Function.prototype`).

**Special JS Feature/Syntax**

The `at()` method is a relatively recent addition to the JavaScript standard (ECMAScript 2020). It was introduced to provide a more expressive and object-like way to access elements in arrays, but its usage in strings is still not as common.

**Other Alternatives**

For accessing the last character of a string:

* **Using `str.length - 1`**: Similar to the char index method, but using arithmetic instead of indexing.
* **Using regular expressions**: With `RegExp.prototype.exec()`, which can be more flexible than direct access methods.

However, these alternatives are not directly comparable to the four methods being tested in this benchmark.

Related benchmarks:

Last char in a string: char index vs charAt() vs slice() vs at() (version: 1)

Compare methods for testing string's beggining character.

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

Created: one year ago by: Registered User

Jump to the latest result

character index

charAt()

slice()

at()

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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