Benchmark: charAt vs substr vs substring vs slice test

Script Preparation code:

var str = "The quick brown fox jumps over the lazy dog";

Tests:

charAt
let first_char_charAt = str.charAt(0); let second_char_charAt = str.charAt(1); let last_char_charAt = str.charAt(str.length-1);
substr
let first_char_substr = str.substr(0, 1); let second_char_substr = str.substr(1, 1); let last_char_substr = str.substr(str.length-1, 1);
substring
let first_char_substring = str.substring(0, 1); let second_char_substring = str.substring(1, 2); let last_char_substring = str.substring(str.length-1, str.length);
slice
let first_char_slice = str.slice(0, 1); let second_char_slice = str.slice(1, 2); let last_char_slice = str.slice(str.length-1, str.length);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
charAt
substr
substring
slice

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:103.0) Gecko/20100101 Firefox/103.0

Browser/OS: Firefox 103 on Linux

View result in a separate tab

Test name	Executions per second
charAt	981035648.0 Ops/sec
substr	70237432.0 Ops/sec
substring	17535754.0 Ops/sec
slice	18128424.0 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 details of this JavaScript benchmark.

**Benchmark Definition**

The provided JSON defines a performance test for extracting the first and last characters from a string. The test is designed to measure the execution speed of different string manipulation methods: `charAt`, `substr`, `substring`, and `slice`.

**String Preparation Code**

The script preparation code is identical across all tests, which means that only the comparison method changes:
```javascript
var str = "The quick brown fox jumps over the lazy dog";
```
This ensures that the input string is always the same, allowing for a fair comparison of the different methods.

**Comparison Methods**

Here's what each comparison method does:

1. **`charAt`**: Extracts a single character at a specific index.
2. **`substr`**: Extracts a substring from the start of the original string up to a specified length.
3. **`substring`**: Extracts a substring from the start of the original string up to a specified end index (or the end of the string if no end index is provided).
4. **`slice`**: Creates a new string by extracting a portion of the original string, starting at a specified start index and ending at a specified length.

**Pros and Cons**

Here's a brief summary of the pros and cons of each method:

*   `charAt`: Pros: efficient for single character extraction; Cons: may lead to slower performance if only part of the string is being accessed (due to overhead from calculating the entire length).
    *   In terms of performance, `charAt` can be very efficient as it doesn't require additional memory allocation. It also provides direct access to the individual characters without any overhead.
*   `substr`: Pros: simple and easy to implement; Cons: may lead to slower performance for single character extraction due to unnecessary string creation and copying.
    *   Performance-wise, `substr` can be slow if we're dealing with a short substring because of all the extra allocations that happen during its execution. In terms of simplicity, `substr` is also very straightforward to implement as it's always a simple addition operation.
*   `substring`: Pros: more intuitive than `substr` when extracting substrings; Cons: may lead to slower performance for single character extraction due to unnecessary string creation and copying.
    *   Performance-wise, `substring` has the same issues with performance that `substr` does. However, it provides a clear advantage in terms of simplicity as well as being more intuitive than `substr`.
*   `slice`: Pros: efficient for large substrings; Cons: may lead to slower performance for single character extraction due to unnecessary string creation and copying.
    *   The main benefit of `slice` is that it creates a new array with all the elements from start index (exclusive) up until end index, which can be quite beneficial if we are dealing with large substrings.

**Libraries and Special Features**

None of these methods rely on specific libraries or syntax features. They're built-in JavaScript methods that have been available since the language's inception.

**Other Alternatives**

Here are a few other alternatives you might consider for string manipulation, including:

*   String methods like `indexOf`, `lastIndexOf`, and `split` can also be used to extract parts of a string.
    *   For instance, using `str.indexOf("the")` would return the first index at which "the" appears in the original string. The corresponding character(s) could then be extracted from that index onwards.
*   If you're working with large strings and need faster performance for substring extraction, consider using a library like [JS-String](https://github.com/mikamit/js-string).
    *   JS-String is a small JavaScript library which simplifies common string operations to functions similar in style and syntax to the standard methods.
*   Another alternative is to use regular expressions. For instance, `str.match(/./)[0]` would return the first character of the original string.

These alternatives can provide different benefits depending on your specific requirements and constraints.

Related benchmarks:

charAt vs substr vs substring vs slice test (version: 2)

Performance test of the first and last letters of the string.

Comparing performance of: charAt vs substr vs substring vs slice

Created: 2 years ago by: Registered User

Jump to the latest result

charAt

substr

substring

slice

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):