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:

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

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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: 2 years ago by: Registered User

Jump to the latest result

character index

charAt()

slice()

at()

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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