Benchmark: Fastest way to find keys in objects

Script Preparation code:

source = {
    a: 1,
    b: 2,
    c: 3,
    d: 4,
    e: 5,
    f: 6,
    g: 7,
    h: 8,
};
target = {
    a: 1,
    b: 2,
    d: 4,
    e: 5,
    f: 6,
    i: 9,
    j: 10,
};

Tests:

undefined
for (const sourceKey in source) { if (target[sourceKey] === undefined) { delete target.sourceKey; } }
hasOwnProperty
for (const sourceKey in source) { if (!target.hasOwnProperty(sourceKey)) { delete target.sourceKey; } }
in
for (const sourceKey in source) { if (!(sourceKey in target)) { delete target.sourceKey; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
hasOwnProperty
in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:138.0) Gecko/20100101 Firefox/138.0

Browser/OS: Firefox 138 on Ubuntu

View result in a separate tab

Test name	Executions per second
undefined	13626743.0 Ops/sec
hasOwnProperty	10824985.0 Ops/sec
in	14061618.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark aims to find the fastest way to remove keys from an object in JavaScript. It uses two predefined objects, `source` and `target`, which contain various key-value pairs.

**Options Compared**

Three different approaches are compared:

1. **`in` operator**: This approach checks if a key is present in the object using the `in` operator. If the key is not found, it attempts to delete the non-existent key from the target object.
2. **`hasOwnProperty` method**: This approach uses the `hasOwnProperty` method of the object to check if a property (key) exists. If the key is not found, it attempts to delete the non-existent key from the target object using `delete`.
3. **`undefined` check**: This approach simply checks if the value associated with a key in the source object is `undefined`. If it is, it attempts to delete the corresponding key from the target object.

**Pros and Cons of Each Approach**

1. **`in` operator**:
	* Pros: Simple and efficient.
	* Cons: May not be as fast as other approaches due to its inherent checks.
2. **`hasOwnProperty` method**:
	* Pros: More accurate than the `in` operator, which can return true for inherited properties.
	* Cons: May incur additional overhead due to the method call.
3. **`undefined` check**:
	* Pros: Simple and lightweight.
	* Cons: May not be as efficient as other approaches if the value is not frequently `undefined`.

**Library Usage**

None of the benchmark test cases use a library explicitly, but they do rely on JavaScript's built-in object features (e.g., `in`, `hasOwnProperty`, `delete`).

**Special JS Feature or Syntax**

The benchmark does not explicitly use any special JavaScript features or syntax. However, it relies on some advanced JavaScript concepts, such as:

* Object iteration and traversal (`for...in`)
* Property access and manipulation (`sourceKey`, `target[sourceKey]`, `delete target.sourceKey`)

**Alternatives**

If you're looking for alternative approaches to remove keys from an object in JavaScript, consider the following options:

1. **Using a library**: There are libraries like Lodash or Ramda that provide more efficient and expressive ways to manipulate objects.
2. **Alternative iteration methods**: You can use `Object.keys()` or `Object.entries()` to iterate over the object's properties and remove them individually.
3. **Object pruning**: You can use techniques like Object.prototype.hasOwnProperty.call() to check for the existence of properties, which might be more efficient than using the `in` operator.

Keep in mind that the performance differences between these approaches may be negligible for small objects, but they become significant when dealing with large datasets or complex object hierarchies.

Related benchmarks:

Fastest way to find keys in objects (version: 0)

Fastest way to find keys in objects

Comparing performance of: undefined vs hasOwnProperty vs in

Created: 4 years ago by: Guest

Jump to the latest result

undefined

hasOwnProperty

in

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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