Benchmark: Object key vs Array index access

Script Preparation code:

var obj = {0: 0, 1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 6: 6, 7: 7, 8: 8, 9: 9, 10: 10, 11: 11, 12: 12, 13: 13, 14: 14, 15: 15, 16: 16, 17: 17, 18: 18, 19: 19}
var arr = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]

Tests:

Object
obj[19]
Array
arr[19]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object
Array

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) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Linux

View result in a separate tab

Test name	Executions per second
Object	13893926.0 Ops/sec
Array	14085418.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark test case on the MeasureThat.net website. The benchmark compares two approaches to access an element in an object and an array: using the object's key and using the array index.

**Script Preparation Code**

The script preparation code defines two variables:

1. `obj`: An object with 20 properties, where each property has a corresponding value.
2. `arr`: An array of 20 elements, where each element is a number from 0 to 19.

These variables will be used as the target data for the benchmarking test cases.

**Benchmark Definition**

The benchmark definition consists of two individual test cases:

1. **Object**: The first test case uses the object's key (`obj[19]`) to access the value at index 19.
2. **Array**: The second test case uses the array index (`arr[19]`) to access the value at index 19.

**Library and Purpose**

In both test cases, no external library is used. The `[]` syntax is a built-in JavaScript feature for accessing elements in an array or object by their index.

**Special JS Feature/Syntax**

Neither of these test cases uses any special JavaScript features or syntax that would require additional explanation.

**Pros and Cons of Each Approach**

1. **Object Key**: Using the object's key to access an element has several advantages:
	* It is often more readable and maintainable, especially for large objects.
	* It allows for easier debugging and logging.
	* However, it can be slower than using an array index due to the overhead of property lookup.
2. **Array Index**: Using the array index to access an element has several advantages:
	* It is often faster than using an object key because it avoids the overhead of property lookup.
	* It is more suitable for large arrays or datasets, where accessing elements by their position is common.
	* However, it can be less readable and maintainable, especially for developers not familiar with array indexing.

**Other Alternatives**

For larger objects or datasets, alternative approaches could include:

1. **Using a Map**: If the object's keys are unique and immutable, using a `Map` data structure could provide faster lookups.
2. **Iterating over the Object/Array**: Instead of accessing an element directly by its key or index, iterating over the object or array and checking each property or element individually could be used.
3. **Using a Cache**: If the same elements are accessed repeatedly, using a cache to store the results of previous lookups could improve performance.

Keep in mind that these alternatives may have trade-offs in terms of readability, maintainability, and performance.

Related benchmarks:

Object key vs Array index access (version: 0)

Comparing performance of: Object vs Array

Created: 2 years ago by: Guest

Jump to the latest result

Object

Array

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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