Benchmark: typeof undefined vs undefined equality check

Script Preparation code:

window.obj = undefined

Tests:

equality
window.obj === undefined
typeof
typeof window.obj === 'undefined'

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
equality
typeof

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36

Browser/OS: Chrome 125 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
equality	3758646.0 Ops/sec
typeof	7264546.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

The provided JSON represents a benchmark test on MeasureThat.net, which compares two approaches to check if `undefined` is present in the variable `window.obj`. Here's a breakdown of what's being tested and compared:

**Test Case 1: Equality Check (`window.obj === undefined`)**

* **Purpose:** This test checks for equality between `window.obj` and `undefined`, using the triple equals (`===`) operator.
* **Comparison:** The benchmark compares the execution time of this equality check across different browsers and devices.

**Test Case 2: Type Check with `typeof` (`typeof window.obj === 'undefined'`)**

* **Purpose:** This test checks if the type of `window.obj` is `'undefined'`, using the `typeof` operator.
* **Comparison:** The benchmark compares the execution time of this type check across different browsers and devices.

Now, let's discuss the pros and cons of each approach:

**Equality Check (`window.obj === undefined`)**

Pros:

1. Direct comparison: This approach directly checks if the value is equal to `undefined`, which can be more intuitive.
2. Fewer operations: Equality checks typically involve fewer operations compared to type checks.

Cons:

1. Potential issues with primitive types: Equality checks may not work correctly for primitive types (e.g., numbers, strings) that are also `undefined`.
2. May trigger optimizations: Modern JavaScript engines might optimize equality checks, potentially affecting performance.

**Type Check with `typeof` (`typeof window.obj === 'undefined'`)**

Pros:

1. Robustness: Type checks are less prone to issues with primitive types and can handle more cases.
2. Clarity: The `typeof` operator explicitly states the type of the variable, making it clearer what's being checked.

Cons:

1. Additional operations: Type checks involve more operations compared to equality checks, which might impact performance.
2. Potential differences in behavior: Some JavaScript engines might optimize or handle `typeof` differently than equality checks.

**Library and Special Features**

There are no libraries mentioned in the provided benchmark definition. However, it's worth noting that some JavaScript implementations (e.g., Safari) have specific optimizations for certain types of checks or operators.

**Other Alternatives**

If you're interested in exploring alternative approaches to this benchmark, consider the following:

1. **Regex-based comparison**: Instead of using equality checks or type checks, you could use a regular expression to check if the value is `undefined`. This approach might be more accurate but could also be slower.
2. **Object prototype chain traversal**: You could traverse the object's prototype chain to determine if `window.obj` is `undefined`. This approach would be slower than equality checks but could provide more insight into the object's structure.

Keep in mind that these alternatives might not be suitable for this specific benchmark or might require significant modifications to the original test.

Related benchmarks:

typeof undefined vs undefined equality check (version: 0)

Comparing performance of: equality vs typeof

Created: 5 years ago by: Guest

Jump to the latest result

equality

typeof

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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