Benchmark: undefined vs. typeof vs. in vs. hasOwnProperty 30

Script Preparation code:

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

Tests:

undefined
if(undefined !== obj['d']){}
typeof
if('undefined' !== typeof obj['d']){}
in
if('d' in obj){}
hasOwnProperty
if(obj.hasOwnProperty( 'd' )){}
bool
if(!!obj['d']){}
Undefined2
if(obj['d']!==undefined){}
undefined3
if(obj['d']!=undefined){}
undefined4
if(obj['d']==undefined){}

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool
Undefined2
undefined3
undefined4

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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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 measures the performance of different ways to check if a property exists in an object in JavaScript. The test cases compare the following approaches:

1. `undefined` (directly checking for `undefined`)
2. `typeof` (checking the type of the value using `typeof`)
3. `in` (using the `in` operator)
4. `hasOwnProperty` (specific to objects, checks if the property is a direct property of the object, not inherited from prototype chain)
5. `bool` (a boolean expression `!!obj['d']`, which is true for non-empty strings and objects)
6. Two additional tests with variations in the order of comparison (`undefined2`, `undefined3`, `undefined4`)

**Options Compared**

The benchmark compares the performance of each approach across different devices (Desktop, Windows 10) and browsers (Chrome 78).

**Pros and Cons of Each Approach**

1. **`undefined`**: This is the fastest approach, as it directly checks if a variable is defined or not. However, it may lead to unexpected results when used in certain contexts.
2. **`typeof`**: This method checks the type of the value using `typeof`. While it's generally safe, it can be slower than direct comparison due to its overhead.
3. **`in`**: The `in` operator checks if a property exists in an object or not. It's a simple and fast approach but may lead to unexpected results when used with objects that have inherited properties.
4. **`hasOwnProperty`**: This method is specific to objects and checks if the property is a direct property of the object, not inherited from prototype chain. While it's safer than `in`, it can be slower due to its additional overhead.
5. **`bool`**: The boolean expression `!!obj['d']` is true for non-empty strings and objects. It's a simple and fast approach but may lead to unexpected results when used with other types of values.

**Other Considerations**

* When using `in`, it's essential to be aware that objects in modern JavaScript can have inherited properties, which might affect the performance.
* The `hasOwnProperty` method is not as efficient as direct comparison or `typeof`, but it provides a safer alternative when working with objects.

**Alternative Approaches**

Other approaches to check if a property exists in an object include:

1. Using `Object.prototype.hasOwnProperty.call(obj, 'd')`
2. Checking the length of the array returned by `Object.keys(obj).indexOf('d')`
3. Using a recursive function to traverse the object and its prototype chain.

However, these approaches might be slower or more complex than the methods tested in this benchmark.

Related benchmarks:

undefined vs. typeof vs. in vs. hasOwnProperty 30 (version: 0)

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool vs Undefined2 vs undefined3 vs undefined4

Created: 6 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Undefined2

undefined3

undefined4

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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