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

Script Preparation code:

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

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
truthy
!! obj.d;
local undef
undef !== obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
truthy
local undef

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 23 days ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark is designed to measure the performance of JavaScript objects in different scenarios, specifically:

* `undefined` vs. literal values (e.g., `obj.d`)
* Truthiness (`!! obj.d`)
* Property existence using `in`, `hasOwnProperty`, or `typeof`

This benchmark aims to compare the performance of these different approaches on various browsers and devices.

**Script Preparation Code**

The script preparation code initializes an object `obj` with properties `a`, `b`, `c`, `d`, and `e`. The variable `undef` is assigned a value, which will be used later in the benchmarking process.

**Html Preparation Code**

There is no HTML preparation code provided, so it's likely that the test is designed to run solely on the client-side (JavaScript execution).

**Test Cases**

The individual test cases are defined as follows:

1. `undefined !== obj.d`: Tests the performance of comparing an object property with `undefined`.
2. `'undefined' !== typeof obj.d`: Tests the performance of comparing the type of an object property using `typeof`.
3. `'d' in obj`: Tests the performance of checking if a property exists in an object using the `in` operator.
4. `obj.hasOwnProperty('d')`: Tests the performance of checking if a property exists in an object using the `hasOwnProperty` method.
5. `!! obj.d`: Tests the performance of evaluating an object property as truthy or falsy.
6. `undef !== obj.d`: Tests the performance of comparing two values with different types.

**Library and Special Features**

* There is no library explicitly mentioned in the benchmark definition.
* The use of `typeof` operator is a special feature, which checks the type of a variable or value.
* The use of `in` operator is also a special feature, which checks if a property exists in an object.

**Pros and Cons of Different Approaches**

Here's a brief summary of the pros and cons of each approach:

1. **Comparison with `undefined`**: This approach can be faster because it uses a simple comparison operation. However, it may not be as accurate as other approaches.
2. **Comparison with `typeof`**: This approach is more accurate than comparing with `undefined` but slower due to the overhead of type checking. It's suitable for cases where accuracy is more important than performance.
3. **Property existence using `in` operator**: This approach can be faster than `hasOwnProperty`, but it may not be as accurate, as some properties might be inherited from parent objects.
4. **Property existence using `hasOwnProperty`**: This approach is more accurate than `in` operator because it only checks if the property exists in the object's own property table, excluding inherited properties.
5. **Truthiness evaluation**: This approach can be faster than comparing with `undefined`, but it may not be as intuitive for some developers.

**Other Alternatives**

Some alternative approaches to evaluate object properties include:

* Using a `for...in` loop to iterate over the object's property names
* Using the `Object.keys()` and `Array.prototype.includes()` methods to check if a property exists
* Using a library like Lodash or Moment.js to perform more complex operations on objects

It's worth noting that these alternatives might not be as efficient or accurate as the approaches used in the benchmarking test.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.0 Safari/605.1.15

Browser/OS: Safari 15 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
undefined	9405947.0 Ops/sec
typeof	26169084.0 Ops/sec
in	26041106.0 Ops/sec
hasOwnProperty	25609274.0 Ops/sec
truthy	26193902.0 Ops/sec
local undef	13944701.0 Ops/sec

Related benchmarks:

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

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs truthy vs local undef

Created: 7 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

truthy

local undef

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 23 days ago):