Benchmark: char index vs charAt() vs slice() for the last character

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();

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: 2 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:130.0) Gecko/20100101 Firefox/130.0

Browser/OS: Firefox 130 on Windows

View result in a separate tab

Test name	Executions per second
character index	104625000.0 Ops/sec
charAt()	99724600.0 Ops/sec
slice()	85370144.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the provided benchmarking test case.

**Benchmark Overview**

The benchmark is designed to compare the performance of three different methods for accessing the last character in a string:

1. `charIndex` (character index)
2. `charAt()` (characterAt() method)
3. `slice()` (slice() method)

**Options Compared**

Here are the options being compared, along with their pros and cons:

* **charIndex**: This approach involves directly indexing into the string using square brackets (`str[str.length-1]`). The advantages of this method include:
	+ Simple and straightforward syntax.
	+ Low overhead due to no function call or object lookup.
	However, its main disadvantage is that it requires an integer value as a key, which can be slower than other methods when dealing with large strings.
* **charAt()**: This approach involves calling the `charAt()` method on the string object and passing in the index of the desired character (`str.charAt(str.length-1)`). The advantages of this method include:
	+ More readable syntax compared to charIndex.
	+ Often preferred by developers due to its familiarity with the DOM.
However, its main disadvantage is that it involves a function call, which can introduce overhead.
* **slice()**: This approach involves calling the `slice()` method on the string object and passing in an index of 0 and the desired length (`str.slice(-1)`). The advantages of this method include:
	+ Often faster than charIndex due to its ability to avoid integer arithmetic.
However, its main disadvantage is that it requires a function call, which can introduce overhead.

**Library Used**

The `noop` variable is assigned a new function using `Function.prototype`, but in this context, it's not actually used anywhere. It's likely included as a placeholder or for performance testing purposes.

**Special JS Feature/Syntax**

None of the test cases explicitly use any special JavaScript features or syntax that would require additional explanation.

**Other Considerations**

When benchmarking string access methods, it's essential to consider factors like:

* String length: Longer strings may favor methods with lower overhead.
* Browser and engine differences: Different browsers or engines might optimize these methods differently.
* CPU architecture: Some architectures might be more efficient for certain operations than others.

**Alternatives**

Other alternatives for accessing the last character in a string could include using a regular expression (e.g., `/(.)$/`) or exploiting properties like `length` and indexing (`str[str.length-1]`). However, these approaches may not be as straightforward or readable as the methods being compared in this benchmark.

Overall, the benchmark provides a useful comparison of three common methods for accessing the last character in a string, allowing developers to make informed decisions about which approach best suits their needs.

Related benchmarks:

char index vs charAt() vs slice() for the last character (version: 0)

Compare methods for testing string's last character.

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

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 6 months ago):