Benchmark: is variable undefined? typeof variable === "undefined" vs variable === undefined

is variable undefined? typeof variable === "undefined" vs variable === undefined (version: 0) Benchmark.js

Comparing whether checking is (typeof variable === "undefined") is faster than (variable === undefined)

Comparing performance of: `typeof string is undefined vs typeof undefined is undefined vs string is undefined vs undefined is undefined`

Created: 5 years ago by: Guest

Go to the latest result

Tests:

typeof string is undefined
typeof "not undefined" === "undefined"
typeof undefined is undefined
typeof undefined === "undefined"
string is undefined
"not undefined" === undefined
undefined is undefined
undefined === undefined

Historical Performance Data aggregated from 32 community runs

Desktop Results:

Chrome 27 runs

typeof string is undefined

152.3M/s

string is undefined

12.7M/s

typeof undefined is undefined

12.5M/s

undefined is undefined

6.5M/s

Fastest: typeof string is undefined (23.5x faster)

View exact numbers

✓ typeof string is undefined: 152,348,896 ops/sec
• string is undefined: 12,741,343 ops/sec
• typeof undefined is undefined: 12,469,086 ops/sec
• undefined is undefined: 6,486,746 ops/sec

Firefox 5 runs

typeof string is undefined

1133.1M/s

string is undefined

1119.7M/s

undefined is undefined

1095.5M/s

typeof undefined is undefined

1017.3M/s

Fastest: typeof string is undefined (1.1x faster)

View exact numbers

✓ typeof string is undefined: 1,133,128,832 ops/sec
• string is undefined: 1,119,731,072 ops/sec
• undefined is undefined: 1,095,505,792 ops/sec
• typeof undefined is undefined: 1,017,315,904 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
typeof string is undefined
typeof undefined is undefined
string is undefined
undefined is undefined

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/134.0.0.0 Safari/537.36

Browser/OS: Chrome 134 on Mac OS X 10.15.7

View result in a separate tab

undefined is undefined

244.0M/s

typeof string is undefined

235.5M/s

string is undefined

226.7M/s

typeof undefined is undefined

224.2M/s

View exact numbers

Test name	Executions per second
✓ undefined is undefined	243,970,304 Ops/sec
typeof string is undefined	235,450,816 Ops/sec
string is undefined	226,660,032 Ops/sec
typeof undefined is undefined	224,156,416 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested on the provided JSON data.

The benchmark is testing two approaches for checking if a variable is undefined:

1. `typeof variable === "undefined"` (Method 1)
2. `variable === undefined` (Method 2)

**Options Comparison**

Both methods are used to check if a variable is undefined, but they differ in how the comparison is performed.

* **Method 1: `typeof variable === "undefined"`**
	+ This method uses the `typeof` operator to get the type of the variable.
	+ It then checks if the result is equal to `"undefined"`.
	+ This approach can be slower because it involves an additional operation (getting the type).
* **Method 2: `variable === undefined`**
	+ This method directly compares the variable with `undefined`.
	+ This approach is often faster because it's a simple equality check.

**Pros and Cons**

* **Method 1 (typeof)**:
	+ Pros: Can be useful in certain situations where you need to get the type of a variable before comparing it.
	+ Cons: Generally slower due to the additional operation.
* **Method 2 (direct comparison)**:
	+ Pros: Faster because it's a simple equality check.
	+ Cons: May not work correctly for all variables (e.g., if `undefined` is not a primitive value).

**Other Considerations**

Both methods can be affected by the type of variable being checked. For example:

* If the variable is an object, `typeof variable === "object"` might return `"object"`, rather than `"undefined"`.
* If the variable is set to `null`, both methods will return `false`.

**Library and Special JS Features**

None of the tests appear to use a specific library or special JavaScript features.

**Benchmark Preparation Code**

The preparation code for each test case is not provided, but it's likely that they involve setting up variables with different types (e.g., strings, numbers, undefined) and running the benchmark multiple times to get accurate results.

**Other Alternatives**

If you want to explore other approaches to checking if a variable is undefined, consider:

* Using `hasOwnProperty` on an object: `if (variable.hasOwnProperty("constructor")) { ... }`
* Using `instanceof`: `if (!(variable instanceof Object)) { ... }`
* Using a library like Lodash's `isUndefined` function

Keep in mind that these alternatives might not provide the same level of performance as Method 2, but they can offer more flexibility or correctness in certain situations.

is variable undefined? typeof variable === "undefined" vs variable === undefined (version: 0) Benchmark.js

Comparing whether checking is (typeof variable === "undefined") is faster than (variable === undefined)

Comparing performance of: typeof string is undefined vs typeof undefined is undefined vs string is undefined vs undefined is undefined

Created: 5 years ago by: Guest

Go to the latest result

typeof string is undefined

typeof undefined is undefined

string is undefined

undefined is undefined

Historical Performance Data aggregated from 32 community runs

Desktop Results:

Chrome 27 runs

Firefox 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `typeof string is undefined vs typeof undefined is undefined vs string is undefined vs undefined is undefined`