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Undefined testing
(version: 0)
Comparing performance of:
typeof x === "undefined" vs x === undefined
Created:
9 years ago
by:
Guest
Jump to the latest result
Script Preparation code:
var x; var y = {};
Tests:
typeof x === "undefined"
typeof x === "undefined"
x === undefined
x === undefined
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
typeof x === "undefined"
x === undefined
Fastest:
N/A
Slowest:
N/A
Latest run results:
No previous run results
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the benchmark and its options. **Benchmark Definition** The benchmark is defined by two scripts: one for preparing the test environment (`Script Preparation Code`) and another empty string (`Html Preparation Code`). The purpose of these scripts seems to be minimal, only setting up a variable `x` as undefined. **Options Compared** There are two options being compared: 1. `typeof x === "undefined"` 2. `x === undefined` Both expressions check if `x` is undefined, but they do so in different ways. **Pros and Cons** * **`typeof x === "undefined"`** + Pros: - More concise and readable. - Less vulnerable to type coercion issues (e.g., `null` and `undefined` are treated as distinct values). + Cons: - May not be optimized by the JavaScript engine, which might lead to a performance hit compared to the second option. * **`x === undefined`** + Pros: - Might be more efficient due to potential optimizations in the JavaScript engine. + Cons: - Less readable and more prone to type coercion issues. **Library** There is no library explicitly mentioned in this benchmark. However, it's worth noting that some modern JavaScript engines might use techniques like "opt-in" or "opt-out" optimization for `typeof` checks, which could affect the performance of these expressions. **Special JS Feature/Syntax** None are explicitly mentioned in this benchmark. However, if you were to add any special features or syntax (e.g., ES6+ classes, async/await), it would impact how the test is executed and interpreted by the JavaScript engine. **Other Alternatives** If you wanted to explore alternative approaches, here are a few: * Using `x == undefined` instead of `typeof x === "undefined"`. * Adding additional checks for specific values (e.g., `x == null`, `x == undefined || x == null`). * Comparing the execution time of different libraries or frameworks that implement JavaScript engine optimizations. * Investigating how other programming languages or runtimes handle similar checks. Keep in mind that altering these tests could significantly impact their accuracy and reliability, so it's essential to understand the underlying assumptions and potential pitfalls.
Related benchmarks:
Undefined testing
undefined checking
typeof undefined vs === undefined
Comparing null vs undefined
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