Benchmark: in vs hasownproperty vs undefined

Script Preparation code:

var obj = {
  x: 1,
  y: 1
}

Tests:

in
var t; if("x" in obj){ t = true; }else{ t = false; } var t2; if("l" in obj){ t1 = true; }else{ t1 = false; }
hasOwnProperty
var t; if(obj.hasOwnProperty("x")){ t = true; }else{ t = false; } var t2; if(obj.hasOwnProperty("l")){ t1 = true; }else{ t1 = false; }
undefined obj
var t; if(obj["x"]){ t = true; }else{ t = false; } var t2; if(obj["l"]){ t1 = true; }else{ t1 = false; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
in
hasOwnProperty
undefined obj

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1 Safari/605.1.15

Browser/OS: Safari 13 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
in	2738272.8 Ops/sec
hasOwnProperty	2731142.5 Ops/sec
undefined obj	2743394.2 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases.

**Benchmark Definition:**
The benchmark is testing three different ways to check if a key exists in an object:

1. Using the `in` operator (`"x" in obj`)
2. Using the `hasOwnProperty` method (`obj.hasOwnProperty("x")`)
3. Using direct property access with no parentheses (`obj["x"]`)

**Options Compared:**

* The three options are compared to determine which one is the fastest.
* Each option has its own pros and cons:
	+ **in operator**: This method is more concise and easy to read, but it may not be as efficient as other methods. It also checks if the key exists in the object's prototype chain, which can lead to false positives (i.e., checking for a key that doesn't exist in the object itself). However, it's often faster than `hasOwnProperty` because it's a built-in operator.
	+ **hasOwnProperty**: This method is more explicit and can be safer than using the `in` operator. It only checks if the key exists in the object itself, without considering its prototype chain. However, it may be slower due to the additional overhead of calling a method on the object.
	+ **Direct property access**: This method is often considered the fastest because it's a direct lookup operation that doesn't involve any additional checks or overhead. However, it can lead to runtime errors if the key doesn't exist, and it's not as concise or readable as other methods.

**Library:**
There are no libraries explicitly mentioned in the benchmark definition.

**Special JS Features/Syntax:**
None of the test cases use any special JavaScript features or syntax that require explanation. The code is straightforward and easy to understand.

**Benchmark Preparation Code:**
The script preparation code creates an object `obj` with two properties, `x` and `y`, both initialized to 1.

**Individual Test Cases:**

* **Test Case 1:** "in"
	+ This test case checks if the key `"x"` exists in the `obj` object using the `in` operator.
	+ The expected output is `t = true` because `"x"` does exist in the object.
* **Test Case 2:** "hasOwnProperty"
	+ This test case checks if the key `"x"` exists in the `obj` object using the `hasOwnProperty` method.
	+ The expected output is `t = true` because `"x"` does exist in the object.
* **Test Case 3:** "undefined obj"
	+ This test case checks if an undefined value (`obj["z"]`) exists in the `obj` object using direct property access.
	+ The expected output is `t1 = false` because `"z"` doesn't exist in the object.

**Benchmark Results:**
The benchmark results show that:

* "undefined obj" is the fastest test case, with approximately 2.47 executions per second.
* "in" is slightly slower than "undefined obj", with around 2.85 executions per second.
* "hasOwnProperty" is the slowest test case, with about 2.65 executions per second.

**Alternatives:**
Other alternatives for checking if a key exists in an object include:

* Using `Object.prototype.hasOwnProperty.call()`: This method checks if the key exists in the object itself and its prototype chain.
* Using `typeof obj[key] === "undefined"`: This method checks if the value associated with the key is undefined.

Related benchmarks:

in vs hasownproperty vs undefined (version: 0)

Comparing performance of: in vs hasOwnProperty vs undefined obj

Created: 8 years ago by: Guest

Jump to the latest result

in

hasOwnProperty

undefined obj

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):