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

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

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: 4 years ago by: Guest

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Tests:

typeof string is undefined
let x = "not undefined"; typeof x === "undefined"
typeof undefined is undefined
let x; typeof x === "undefined"
string is undefined
let x = "not undefined"; x === undefined
undefined is undefined
let x; x === undefined

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:

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

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I'll break down the benchmark definition and options being compared, along with their pros and cons.

**Benchmark Definition**

The benchmark measures which approach is faster for checking if a variable is `undefined`. The two approaches are:

1. `typeof variable === "undefined"` (Type of operator)
2. `variable === undefined` (Direct comparison)

**Options Compared**

There are four test cases that compare these two approaches, each with a different variable type:

1. `let x = "not undefined";`
	* `typeof x === "undefined"`
	* `x === undefined`
2. `let x;`
	* `typeof x === "undefined"`
	* `x === undefined`

**Pros and Cons**

### Type of Operator (`typeof variable === "undefined"`)

Pros:

1. More explicit and readable.
2. Less error-prone, as it's a built-in operator.

Cons:

1. Slower due to the overhead of the type checking process.
2. Not supported in older browsers or environments that don't have the `typeof` operator (e.g., some mobile devices).

### Direct Comparison (`variable === undefined`)

Pros:

1. Faster, as it's a simple equality check.
2. More likely to be supported in older browsers and environments.

Cons:

1. Less explicit and less readable.
2. Error-prone, as it relies on the variable being exactly equal to `undefined`, which can lead to unexpected behavior if not handled correctly.

**Other Considerations**

* The benchmark results show that the Type of Operator approach is consistently slower than the Direct Comparison approach.
* However, in some cases (e.g., test case 3), the Direct Comparison approach is even slower due to an optimization issue in Chrome's `typeof` implementation.
* It's essential to note that these results might vary depending on the specific use case and environment.

**Alternative Approaches**

1. **Using a different type of operator**: Instead of comparing to `"undefined"`, you could use `typeof variable === 'undefined'` (note the single quotes) or compare to `NaN` for numbers (`variable !== NaN`). These approaches might be faster, but they also depend on the specific language and browser implementation.
2. **Using a helper function**: You can create a helper function that handles the comparison internally, providing more control over the comparison process and potentially reducing overhead.

In conclusion, while the Type of Operator approach is more explicit and readable, the Direct Comparison approach is faster due to its simplicity. However, it's essential to weigh these trade-offs based on your specific use case and requirements.

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