Benchmark: char index vs charAt() vs slice() vs char array index

Script Preparation code:

var str = 'foo bar baz';
var arr = str.split('');
var noop = Function.prototype;

Tests:

character index
if (str[0] == 'f') noop();
charAt()
if (str.charAt(0) == 'f') noop();
slice()
if (str.slice(0, 1) == 'f') noop();
Array index
if (arr[0] == 'f') noop();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36

Browser/OS: Chrome 118 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
character index	7437750.5 Ops/sec
charAt()	7496228.5 Ops/sec
slice()	7494300.0 Ops/sec
Array index	7555058.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**Benchmark Purpose**

The purpose of this benchmark is to compare the performance of different methods for accessing the first character of a string in JavaScript. The test cases evaluate three primary approaches:

1.  **Character Index**: Directly indexing into the string using square brackets `[]`.
2.  **`charAt()`**: Using the `charAt()` method provided by the String prototype.
3.  **`slice()`**: Using the `slice()` method to extract a subset of the string.

**Options Compared**

The benchmark compares these three approaches for accessing the first character of a string:

*   `str[0]`: Character Index, which directly accesses the first element of the string using square brackets.
*   `str.charAt(0)`: `charAt()`, which uses the `charAt()` method provided by the String prototype to access the first character.
*   `str.slice(0, 1)`: `slice()`, which extracts a subset of the string starting from index 0 with a length of 1.

**Pros and Cons**

Here's a brief overview of each approach:

### Character Index (`str[0]`)

*   **Pros**:
    *   Direct access to the first character, potentially faster since it doesn't involve method calls.
    *   Less overhead compared to using methods like `charAt()` or `slice()`.
*   **Cons**:
    *   May not be supported by all JavaScript engines or browsers that don't implement standard string indexing behavior.

### `charAt()` Method

*   **Pros**:
    +   Standardized method provided by the String prototype, widely supported across browsers and engines.
    *   Can handle strings of any length, including very large ones.
*   **Cons**:
    *   Involves a method call, which can introduce overhead compared to direct indexing.
    *   May be slower for short strings due to the additional operation.

### `slice()` Method

*   **Pros**:
    +   Provides a flexible way to extract subsets of strings and is useful when working with longer strings.
    *   Standardized method provided by the String prototype, widely supported across browsers and engines.
*   **Cons**:
    *   Involves a method call, which can introduce overhead compared to direct indexing.
    *   May be slower for very short strings since it needs to perform additional checks.

**Library Usage**

There are no libraries used in this benchmark. The standard JavaScript String prototype is used across all test cases.

**Special JS Features or Syntax**

None of the provided benchmarks use special JavaScript features or syntax that's not widely supported. However, keep in mind that certain browsers or engines may have nuances or variations in how they implement standard JavaScript functionality.

**Other Alternatives**

In a real-world scenario, you might consider alternatives like using regular expressions (`/^\w+/`) to extract the first character of a string. This approach can be more flexible but is also less efficient and might require additional processing steps.

Keep in mind that performance benchmarks often have trade-offs between simplicity, readability, and execution speed. Depending on your specific requirements and constraints, you may need to evaluate different approaches and prioritize factors such as maintainability, efficiency, and compatibility across various browsers and engines.

In conclusion, the provided benchmark provides a useful comparison of three common methods for accessing the first character of a string in JavaScript: direct indexing using square brackets, `charAt()` method, and `slice()` method.

Related benchmarks:

char index vs charAt() vs slice() vs char array index (version: 0)

Compare methods for testing string's beggining character.

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

Created: one year ago by: Registered User

Jump to the latest result

character index

charAt()

slice()

Array index

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):