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

Script Preparation code:

var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 };
function hasOwn (obj, key) {
  return hasOwnProperty.call(obj, key)
}

Tests:

undefined
undefined !== obj.d;
typeof
'undefined' !== typeof obj.d;
in
'd' in obj;
hasOwnProperty
obj.hasOwnProperty( 'd' );
bool
!! obj.d;
Object.prototype.hasOwnProperty
hasOwn(obj, 'd')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
undefined
typeof
in
hasOwnProperty
bool
Object.prototype.hasOwnProperty

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 14 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.84 Safari/537.36

Browser/OS: Chrome 99 on Windows

View result in a separate tab

Test name	Executions per second
undefined	296847232.0 Ops/sec
typeof	508150528.0 Ops/sec
in	587390016.0 Ops/sec
hasOwnProperty	88553664.0 Ops/sec
bool	626298240.0 Ops/sec
Object.prototype.hasOwnProperty	44279072.0 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 and explain what's being tested, compared, and their pros/cons.

**Benchmark Overview**

The benchmark measures the performance of different approaches for object lookup in JavaScript. The script preparation code defines an object `obj` with properties `a`, `b`, `c`, `d`, and `e`. Each test case uses a specific approach to check if a certain property exists or not.

**Test Cases**

Here's a brief explanation of each test case:

1. **undefined**: Checks if the value of `obj.d` is undefined.
2. **typeof**: Compares the type of `obj.d` with `'undefined'`.
3. **in**: Uses the `in` operator to check if `obj.d` exists in the object.
4. **hasOwnProperty**: Calls the `hasOwnProperty` method on the `Object.prototype` to check if `obj.d` exists as a property.
5. **bool**: Checks if the value of `obj.d` is truthy (not falsy) using the double-not operator (`!!`).
6. **Object.prototype.hasOwnProperty**: Similar to `hasOwnProperty`, but uses the prototype chain.

**Comparison**

The benchmark compares the performance of these six approaches:

1. Using an explicit check for undefined (`undefined !== obj.d`)
2. Comparing with a string literal (`'undefined' !== typeof obj.d`)
3. Using the `in` operator
4. Calling the `hasOwnProperty` method on the `Object.prototype`
5. Checking for truthiness using the double-not operator (`!! obj.d`)
6. Checking if the property exists in the prototype chain using `Object.prototype.hasOwnProperty`

**Pros and Cons**

Here's a brief summary of each approach:

1. **Explicit check for undefined**: Fast, but may be less readable.
2. **Comparing with a string literal**: Similar performance to explicit check, but more readable.
3. **Using the `in` operator**: Slow due to its loose equality semantics.
4. **Calling `hasOwnProperty` on `Object.prototype`**: Slow due to prototype chain lookup.
5. **Checking for truthiness using `!!`**: Fast and concise, but may be less readable.
6. **Checking if property exists in prototype chain using `Object.prototype.hasOwnProperty`**: Similar performance to explicit check, but more readable.

**Library Used**

The `hasOwnProperty` method is used from the `Object.prototype`. This method is a part of the ECMAScript standard and is widely supported by most JavaScript engines.

There are no special JS features or syntax used in this benchmark. The tests focus on the performance of different approaches for object lookup.

**Alternatives**

If you need to measure performance in other areas, consider exploring the following alternatives:

1. **Benchmarking libraries**: Libraries like Benchmark.js or Microbenchmark provide more advanced features and flexibility.
2. **Native browser APIs**: Use native browser APIs like `performance.now()` or `PerformanceObserver` for measuring performance.
3. **ES6+ features**: Experiment with modern ES6+ features, such as async/await, Promises, or Web Workers, which can impact performance in different ways.

Keep in mind that benchmarking is an art, and the choice of approach depends on your specific use case and goals.

Related benchmarks:

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

Object lookup performance

Comparing performance of: undefined vs typeof vs in vs hasOwnProperty vs bool vs Object.prototype.hasOwnProperty

Created: 6 years ago by: Guest

Jump to the latest result

undefined

typeof

in

hasOwnProperty

bool

Object.prototype.hasOwnProperty

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):