Benchmark: undefined vs typeof vs !!

Script Preparation code:

var value;

Tests:

strict
value !== undefined
typeof
typeof value !== "undefined"
!!
!!value
void 0;
value !== void 0;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
strict
typeof
!!
void 0;

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36 Edg/130.0.0.0

Browser/OS: Chrome 130 on Windows

View result in a separate tab

Test name	Executions per second
strict	148639696.0 Ops/sec
typeof	191992928.0 Ops/sec
!!	191977520.0 Ops/sec
void 0;	198056752.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided benchmark is designed to compare the performance of three different JavaScript operators: `undefined`, `typeof`, and the double exclamation mark operator (`!!`). The test measures which approach is faster, with a specific focus on handling the `undefined` value.

**Test Cases and Operators**

The benchmark includes four individual test cases:

1. `strict`: This test case uses the strict equality operator (`===`) to check if the value is not equal to `undefined`. However, in the provided benchmark definition, this test case is modified to simply check if `value` is not equal to `undefined`, which makes it vulnerable to false positives.
2. `typeof`: This test case checks if the type of `value` is not equal to `"undefined"`.
3. `!!`: This test case uses the double exclamation mark operator to negate the value and then check if it's not equal to `undefined`.
4. `void 0`: This test case uses the old-fashioned way of checking for an undefined value, by comparing it to the string literal `"void 0"`.

**Comparison and Performance**

The benchmark compares the performance of these four approaches in terms of execution speed, measured in executions per second (ExecutionsPerSecond).

Here's a brief analysis of each approach:

* `strict`: This approach uses the strict equality operator, which is generally considered more efficient than the loose equality operator (`==`). However, due to the modification in the benchmark definition, this test case may not accurately represent the real-world scenario where you might want to check if a value is undefined without using the `===` operator.
* `typeof`: This approach uses the `typeof` operator to check the type of `value`. While it's generally faster than using equality operators, it can be slower than direct checks for `undefined` due to the additional overhead of determining the type.
* `!!`: The double exclamation mark operator is a unary negation operator that converts its operand to a boolean value. This approach is often used as a quick way to check if a value is truthy or falsy, but it can be slower than direct checks for `undefined` due to the additional overhead of the conversion.
* `void 0`: This old-fashioned way of checking for an undefined value is generally considered less efficient and more error-prone than using modern JavaScript operators.

**Pros and Cons**

Here are some pros and cons of each approach:

* `strict`:
	+ Pros: Generally faster and more efficient than equality operators.
	+ Cons: May not accurately represent real-world scenarios where loose equality operators are used.
* `typeof`:
	+ Pros: Faster than direct checks for `undefined`.
	+ Cons: Can be slower than direct checks due to the additional overhead of determining the type.
* `!!`:
	+ Pros: Often used as a quick way to check if a value is truthy or falsy.
	+ Cons: Can be slower than direct checks due to the additional overhead of conversion.
* `void 0`:
	+ Pros: None.
	+ Cons: Generally less efficient and more error-prone than modern JavaScript operators.

**Alternatives**

If you don't want to use these specific approaches, here are some alternative ways to check for an undefined value:

1. Use the nullish coalescing operator (`??`) with a default value: `value ?? defaultValue`.
2. Use the Optional Chaining Operator (`?.`) with a fallback expression: `value?.fallbackExpression`.
3. Use the `in` operator or the `hasOwnProperty()` method to check if an object has a property: `if (value in obj)` or `if (obj.hasOwnProperty(value))`.
4. Use a function that checks for undefined values, such as `function isUndefined(value) { return value === undefined; }`.

Note that these alternatives may have different performance characteristics and use cases compared to the original approaches.

Related benchmarks:

undefined vs typeof vs !! (version: 0)

undefined vs typeof vs !!

Comparing performance of: strict vs typeof vs !! vs void 0;

Created: 3 years ago by: Guest

Jump to the latest result

strict

typeof

!!

void 0;

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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