Benchmark: Array.includes vs. Object key lookup vs. Set.has

Script Preparation code:

var a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
var b = {1: true, 2: true, 3: true, 4: true, 5: true, 6: true, 7: true, 8: true, 9: true, 10: true}
var c = new Set(a);

Tests:

includes
return a.includes(9)
key lookup
return !!b['9']
Set.has
return c.has(9)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
includes
key lookup
Set.has

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/139.0.0.0 Safari/537.36

Browser/OS: Chrome 139 on Mac OS X 10.15.7

View result in a separate tab

Set.has

254.5M/s

key lookup

246.4M/s

includes

130.5M/s

View exact numbers

Test name	Executions per second
✓ Set.has	254,486,272 Ops/sec
key lookup	246,438,320 Ops/sec
includes	130,454,528 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview**

The provided benchmark measures the performance of three different approaches to check if a specific value exists in an array or object: `Array.includes()`, `Object key lookup` (using the `!!` operator), and `Set.has()`.

**Tested Approaches**

1. **Array.includes()**: This method checks if a specified value (`9`) is present in the array `a`.
2. **Object Key Lookup**: This approach uses the `!!` operator to check if the key `'9'` exists in the object `b`. The `!!` operator converts its operand to a boolean value, where `true` becomes 1 and `false` becomes 0. Since the property '9' exists in the object, this expression evaluates to `!!true`, which is equivalent to 1 (truthy). In JavaScript, any non-zero value is considered true in a boolean context.
3. **Set.has()**: This method checks if the element (`9`) is present in the set `c`.

**Pros and Cons of Each Approach**

*   **Array.includes():**
    *   Pros:
        *   Widely supported by modern browsers
        *   Fast performance for large arrays (averaging O(n) time complexity)
        *   Easy to use and understand
    *   Cons:
        *   Slower than `Set.has()` for very small sets or arrays with a single element
*   **Object Key Lookup:**
    *   Pros:
        *   Often faster than `Array.includes()` due to caching optimizations in modern browsers
        *   Suitable for objects where the value is not just a boolean (e.g., using `in` operator)
    *   Cons:
        *   Less intuitive and harder to understand compared to `Array.includes()`
        *   Not suitable for all use cases, as it can lead to unexpected behavior if not used correctly
*   **Set.has():**
    *   Pros:
        *   Fastest approach (averaging O(1) time complexity)
        *   Suitable for sets where the element is only present once
    *   Cons:
        *   Less intuitive and harder to understand compared to `Array.includes()`
        *   Requires a set data structure, which may not be necessary or efficient in all cases

**Library: Set**

The `Set` object is a built-in JavaScript data structure that stores unique values. It's implemented as an unordered collection of key-value pairs, where each value is associated with at most one key. In this benchmark, the set `c` contains the elements from array `a`. The `Set.has()` method checks if a specified element is present in the set.

**Special JavaScript Feature: None**

There are no special JavaScript features or syntax used in this benchmark beyond the standard methods and data structures discussed above.

**Alternatives**

Other alternatives for checking if an element exists in an array or object include:

*   **`in` operator**: Similar to `Object Key Lookup`, but uses a different syntax (`a['9']` instead of `!!b['9']`) and may have different performance characteristics.
*   **Regular expressions (regex)**: Can be used for pattern matching, but may not be the most efficient or intuitive approach in this specific use case.
*   **Custom implementation**: Depending on the specific requirements, you might need to implement a custom algorithm for checking if an element exists in an array or object.

Array.includes vs. Object key lookup vs. Set.has (version: 0)

Comparing performance of: `includes vs key lookup vs Set.has`

Created: 4 years ago by: Guest

Go to the latest result

includes

key lookup

Set.has

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Array.includes vs. Object key lookup vs. Set.has (version: 0)

Comparing performance of: includes vs key lookup vs Set.has

Created: 4 years ago by: Guest

Go to the latest result

includes

key lookup

Set.has

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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Comparing performance of: `includes vs key lookup vs Set.has`