Benchmark: char index vs charAt() vs slice() vs startsWith() vs RegExp (FIXED)

Script Preparation code:

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

Tests:

character index
if (str[0] === '!') noop();
charAt()
if (str.charAt(0) === '!') noop();
startsWith()
if (str.startsWith('!')) noop();
slice()
if (str.slice(0, 1) === '!') noop();
RegExp
if (/^!/.test(str)) noop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
character index
charAt()
startsWith()
slice()
RegExp

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Windows

View result in a separate tab

Test name	Executions per second
character index	15230623.0 Ops/sec
charAt()	15272254.0 Ops/sec
startsWith()	15320079.0 Ops/sec
slice()	15289878.0 Ops/sec
RegExp	12558911.0 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 benchmark and explain what is being tested.

**Benchmark Definition**

The benchmark is designed to compare five different methods for testing the beginning character of a string:

1. **Character Index**: Using the index of the first character (`str[0]`)
2. **`charAt()` Method**: Using the `charAt()` method on the string
3. **`startsWith()` Method**: Using the `startsWith()` method on the string
4. **`slice()` Method**: Using the `slice()` method to extract the first character
5. **Regular Expressions (RegExp)**: Using a regular expression to match the beginning of the string (`/^!/.test(str)`)

**What is being compared?**

Each test case measures the execution speed of each method for testing the beginning character of a fixed input string `str = '!foo bar baz'`. The benchmark aims to determine which method is the fastest.

**Options Compared**

The options compared are:

* Character Index (`str[0]`)
* `charAt()` Method (`str.charAt(0)`)
* `startsWith()` Method (`str.startsWith('!')`)
* `slice()` Method (`str.slice(0, 1)`)
* Regular Expressions (RegExp) (`/^!/.test(str)`)

**Pros and Cons of Each Approach**

Here's a brief summary:

* **Character Index**: Simple and efficient, but may not be supported by all browsers.
* **`charAt()` Method**: Standard method for accessing individual characters in a string, but may have overhead due to function call.
* **`startsWith()` Method**: More readable than `charAt()` or character indexing, but its implementation might vary across browsers.
* **`slice()` Method**: Similar to `charAt()`, but can be used to extract multiple characters at once. However, it may not be the most efficient way to test a single character.
* **Regular Expressions (RegExp)**: Can be slower than other methods due to the overhead of compiling and executing regular expressions.

**Library Used**

In this benchmark, no specific library is explicitly mentioned, but `Function.prototype` is used in the script preparation code (`var noop = Function.prototype;`). This suggests that the benchmark aims to minimize external dependencies.

**Special JS Features or Syntax**

No special JavaScript features or syntax are explicitly mentioned in the benchmark. However, using regular expressions (`RegExp`) requires some basic understanding of regex syntax.

**Other Alternatives**

If these five methods don't meet your requirements or if you need to test other string manipulation functions, consider the following alternatives:

* **String.prototype.indexOf()**: Similar to character indexing but uses a more modern approach.
* **String.prototype.substr()**: Alternative to `slice()` method for extracting substrings.
* **String.prototype.match()**: Can be used with regular expressions to extract substrings or test patterns.

These alternatives might offer different performance profiles, so it's essential to consider your specific use case and requirements.

Related benchmarks:

char index vs charAt() vs slice() vs startsWith() vs RegExp (FIXED) (version: 0)

Compare methods for testing string's beggining character.

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

Created: 2 years ago by: Registered User

Jump to the latest result

character index

charAt()

startsWith()

slice()

RegExp

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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