Benchmark: className.indexOf vs. className.startsWith 1

HTML Preparation code:

<div id="foo" class="test"></div>

Script Preparation code:

var element = document.getElementById("foo");

Tests:

indexOf
element.className.indexOf("test") !== -1
startsWith
element.className.startsWith("test");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
indexOf
startsWith

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Android 10; Mobile; rv:87.0) Gecko/87.0 Firefox/87.0

Browser/OS: Firefox Mobile 87 on Android

View result in a separate tab

Test name	Executions per second
indexOf	9452526.0 Ops/sec
startsWith	12590250.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark is comparing two string comparison methods: `indexOf` and `startsWith`. These methods are part of the JavaScript String prototype.

**Options Compared**

There are two options being compared:

1. **`element.className.indexOf("test") !== -1`**: This option uses the `indexOf` method to search for the substring "test" in the `className` property of the `element` object. If the substring is found, it returns its index (0 if it's at the beginning), and `-1` otherwise.
2. **`element.className.startsWith("test");`**: This option uses the `startsWith` method to check if the string "test" is a prefix of the `className` property.

**Pros and Cons**

*   **`indexOf` Method:**
    *   Pros:
        *   Generally faster, since it only scans until the first occurrence.
        *   Can be more efficient for shorter strings or when searching for a specific substring.
    *   Cons:
        *   Returns `-1` if the substring is not found, which can lead to unnecessary comparisons in subsequent code.
*   **`startsWith` Method:**
    *   Pros:
        *   More intuitive and readable, as it clearly communicates its intent (i.e., checking for a prefix).
        *   Avoids returning `-1`, which simplifies the code path.
    *   Cons:
        *   Can be slower than `indexOf`, since it scans the entire string to find the first occurrence.

**Library and Special JS Features**

There are no libraries mentioned in this benchmark. However, it does use the `document.getElementById` method to retrieve an HTML element by its ID, which is a part of the DOM (Document Object Model) API.

No special JavaScript features or syntax are being tested in this benchmark.

**Other Alternatives**

If you're looking for alternative string comparison methods, consider:

1.  **`includes()` Method**: This is a newer method introduced in ECMAScript 2019 (ES10). It's similar to `indexOf`, but returns a boolean value indicating whether the substring is found, without returning its index.
2.  **Regular Expressions**: You can use regular expressions to search for patterns in strings. However, this approach is generally slower and more complex than the methods mentioned above.

In summary, the benchmark compares two common string comparison methods: `indexOf` and `startsWith`. While both have their pros and cons, `indexOf` tends to be faster but may require additional checks, whereas `startsWith` is more intuitive but potentially slower.

Related benchmarks:

className.indexOf vs. className.startsWith 1 (version: 0)

Comparing performance of: indexOf vs startsWith

Created: 3 years ago by: Guest

Jump to the latest result

indexOf

startsWith

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):