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

Script Preparation code:

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

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
obj.d;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmarking test case, specifically designed to measure the performance of different object lookup methods in JavaScript.

**Object Lookup Methods Compared**

The benchmark compares five different object lookup methods:

1. **`undefined`**: Directly accessing an undefined property on an object.
2. **`typeof`**: Using the `typeof` operator to check the type of a variable or expression, including object properties.
3. **`in`**: Using the `in` operator to test if a property is present in an object.
4. **`hasOwnProperty`**: Using the `hasOwnProperty` method on an object to check if it has a specific property.
5. **`bool`** (not explicitly defined in the code, but likely referring to a boolean literal or comparison): Directly accessing a boolean value.

Each test case measures the performance of one of these methods when applied to the same property (`obj.d`) on an object `obj`.

**Pros and Cons of Each Approach**

1. **`undefined`**: This approach can be fast since it directly accesses the memory location of the property, but it's also prone to errors if not used carefully.
2. **`typeof`**: Using `typeof` can provide more information about the type of property being accessed, but it may incur a small performance overhead due to the operator's execution cost.
3. **`in`**: The `in` operator is generally fast and straightforward, making it a popular choice for object lookup. However, it might not work as expected if the property name is in a non-string format (e.g., numeric).
4. **`hasOwnProperty`**: This method checks if the object has the property as its own property, rather than inheriting it from a prototype chain. While it provides more accurate results, it may be slower due to the additional lookup.
5. **`bool`** (assuming a boolean literal or comparison): Directly accessing a boolean value is likely to be very fast, but it's not applicable in this case since `obj.d` doesn't evaluate to a boolean.

**Library and Purpose**

In this benchmark, none of the libraries are explicitly used. However, it's worth noting that some JavaScript engines may use internal libraries or optimizations for object lookup, which could potentially affect the results of this benchmark.

**Special JS Features and Syntax**

None of the individual test cases appear to exploit any special JavaScript features or syntax, except possibly for the `typeof` operator, which is a built-in operator in JavaScript. However, its usage is straightforward enough that it's not worth highlighting as a unique aspect of these tests.

**Other Alternatives**

Some alternative object lookup methods could be explored in future benchmarks, such as:

* Using `in` with a non-string property name (e.g., a numeric index)
* Employing custom getter or setter functions to manipulate property access
* Utilizing `Object.prototype.hasOwnProperty.call()` or other similar methods
* Testing the performance of different object types (e.g., objects, arrays) or data structures

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36

Browser/OS: Chrome 75 on Linux

View result in a separate tab

Test name	Executions per second
undefined	2906843.2 Ops/sec
typeof	7814792.5 Ops/sec
in	7890009.0 Ops/sec
hasOwnProperty	6599976.0 Ops/sec
bool	7806467.0 Ops/sec

Related benchmarks:

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

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool

Created: 5 years ago by: Registered User

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):