Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty 2

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };

Tests:

in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
in
hasOwnProperty

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:76.0) Gecko/20100101 Firefox/76.0

Browser/OS: Firefox 76 on Linux

View result in a separate tab

Test name	Executions per second
in	147353744.0 Ops/sec
hasOwnProperty	170827392.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided JSON data and explain what's being tested, compared, and discussed in the context of JavaScript microbenchmarks.

**Benchmark Definition**

The benchmark is designed to measure the performance of three different approaches for object lookup:

1. `in`
2. `hasOwnProperty`

**Script Preparation Code**

The script preparation code creates a sample object `obj` with five properties (`a`, `b`, `c`, `d`, and `e`). This object will be used as the test subject for the benchmark.

**Html Preparation Code**

There is no HTML preparation code provided, which means that only JavaScript performance is being measured, without considering factors like rendering or layout.

**Individual Test Cases**

The benchmark consists of two individual test cases:

1. `in`: This test case uses the `in` operator to check if a property (`'d'`) exists in the `obj` object.
2. `hasOwnProperty`: This test case uses the `hasOwnProperty` method to check if an object has a specific own property (`'d'`).

**Library and Purpose**

In this benchmark, no library is explicitly mentioned or used. The only external dependency is JavaScript itself.

**Special JS Feature or Syntax**

The `in` operator and `hasOwnProperty` method are both part of the JavaScript language specification. They provide ways to check for property existence in objects. However, there's an additional feature worth mentioning:

* **WeakMap**: There isn't a direct WeakMap reference used here; however, the in operator is weakly typed which means when you look up properties on an object it does not create new copies of the properties.

**Pros and Cons**

Here are some pros and cons for each approach:

1. `in`:
	* Pros: Easy to use, simple syntax.
	* Cons: Can lead to performance issues if used excessively or in loops, as it performs a lookup on the object's prototype chain.
2. `hasOwnProperty`:
	* Pros: More accurate than `in`, as it only checks the own property of the given object.
	* Cons: May be slower than `in`, especially for large objects.

**Other Alternatives**

In addition to these two approaches, other alternatives for object lookup in JavaScript include:

1. **Bracket notation (`obj['d']`)**: This method is more explicit but can be slower due to the string lookup.
2. **Property access with a getter/setter**: If you're using ES6 classes or modern objects, you might use property access with a getter and setter.

**Alternative Implementation**

Here's an example implementation in JavaScript that demonstrates these alternatives:

```javascript
function objLookup() {
  const obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };

// in operator
  console.log('in operator:', 'd' in obj);

// hasOwnProperty method
  console.log('hasOwnProperty', obj.hasOwnProperty('d'));

// bracket notation
  console.log('bracket notation', obj['d']);

// property access with getter/setter (ES6)
  class Obj {
    constructor() {}
    get d() { return 4; }
  }
  const o = new Obj();
  console.log('property access with getter/setter', o.d);
}

objLookup();
```

This implementation showcases different ways to perform object lookup in JavaScript.

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty 2 (version: 0)

Object lookup performance

Comparing performance of: in vs hasOwnProperty

Created: 6 years ago by: Guest

Jump to the latest result

in

hasOwnProperty

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):