Benchmark: String indexOf vs startsWith/endsWith

Script Preparation code:

var str = "penpineappleapplepen"

Tests:

indexOf
str.indexOf('pen') !== 1
startsWith
str.startsWith('pen')
endsWith
str.endsWith('pen')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
indexOf
startsWith
endsWith

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36

Browser/OS: Chrome 143 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
indexOf	258350128.0 Ops/sec
startsWith	207259552.0 Ops/sec
endsWith	226708400.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll explain the benchmark and its options in detail.

**Benchmark Overview**

The provided benchmark measures the performance of three string methods: `indexOf`, `startsWith`, and `endsWith`. These methods are used to search for a substring within a larger string. The benchmark uses a fixed string `"penpineappleapplepen"` as input, which contains both the target substring ("pen") and its reverse.

**Methods Compared**

The benchmark compares the performance of three different approaches:

1. **`indexOf` method**: This method returns the index of the first occurrence of the specified substring within the string.
2. **`startsWith` method**: This method returns a boolean indicating whether the string starts with the specified substring.
3. **`endsWith` method**: This method returns a boolean indicating whether the string ends with the specified substring.

**Pros and Cons**

*   **`indexOf` method**:
    *   Pros: Fast, as it only scans the input string once to find the first occurrence of the target substring.
    *   Cons: May return -1 if the target substring is not found, which can be misleading. It also uses a linear search algorithm, making it slower for large strings.
*   **`startsWith` and `endsWith` methods**:
    *   Pros: More accurate than `indexOf`, as they only check the first or last characters of the string, respectively. They are also faster than `indexOf` for small substrings.
    *   Cons: May be slower for larger substrings due to the overhead of creating a regex pattern.

**Library and Purpose**

The benchmark uses the JavaScript `String.prototype.indexOf`, `String.prototype.startsWith`, and `String.prototype.endsWith` methods, which are part of the ECMAScript standard. These methods provide a convenient way to search for substrings within strings.

**Special JS Feature or Syntax**

There is no special JavaScript feature or syntax used in this benchmark. However, it does utilize some internal optimizations provided by the JavaScript engine, such as:

*   **String interpolation**: The `str` variable is defined using template literals, which allows for more readable and efficient string concatenation.
*   **Regex pattern optimization**: Although not explicitly shown in the benchmark code, modern JavaScript engines (including Firefox) use regex patterns internally to optimize performance.

**Alternatives**

Other alternatives for searching substrings within strings include:

*   Using a library like Lodash's `str.contains`, which provides more advanced substring search functionality.
*   Implementing custom substring search algorithms using bitwise operations or regular expressions.
*   Utilizing third-party libraries like Squirrelfish (a JavaScript performance optimization library) for optimized string searching.

Keep in mind that these alternatives may not be as efficient as the built-in methods used by modern JavaScript engines.

Related benchmarks:

String indexOf vs startsWith/endsWith (version: 0)

Comparing performance of: indexOf vs startsWith vs endsWith

Created: 5 years ago by: Guest

Jump to the latest result

indexOf

startsWith

endsWith

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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