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undefined vs. typeof vs. in vs. hasOwnProperty with negation similarities
(version: 0)
Object lookup performance
Comparing performance of:
undefined vs typeof vs in vs hasOwnProperty vs bool
Created:
4 years ago
by:
Guest
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Script Preparation code:
var obj = { a: 1, b: 2, c: 3, d: 4, e: 5 }; var k = 'd';
Tests:
undefined
undefined !== obj[k];
typeof
'undefined' !== typeof obj[k];
in
!(k in obj);
hasOwnProperty
obj.hasOwnProperty( k );
bool
! obj[k];
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (5)
Previous results
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Test case name
Result
undefined
typeof
in
hasOwnProperty
bool
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down what's being tested in this benchmark. The benchmark is designed to compare the performance of four different approaches for checking if a property exists in an object: 1. `in`: The `in` operator checks if a property with the given name exists in the object. 2. `typeof` and negation: This approach uses the `typeof` operator to check the type of the variable, and then negates the result using logical NOT (`!`). If the variable is an object property, `typeof` will return `'object'`, which is truthy, so this approach doesn't work as intended. However, if you're only interested in checking if a property exists without caring about its type, this approach might be faster because it avoids the overhead of the `in` operator. 3. `hasOwnProperty`: This method is specifically designed for objects to check if a property exists and is inherited from the prototype chain. It's usually slower than `in` but can be faster when used with modern JavaScript engines that optimize this method. 4. `! obj[k];`: This approach uses logical negation on the result of accessing the object's property directly using square brackets (`obj[k]`). If the property exists, its value will be truthy, so the negation operation will return false, indicating that the property doesn't exist. Now, let's discuss the pros and cons of each approach: * `in` is generally the fastest because it uses a direct lookup in the object's prototype chain. However, it has some quirks, such as returning true for inherited properties or when the object has a non-existent property. * `typeof` and negation is not recommended due to its limitations and potential performance issues. However, if you're only interested in checking existence without caring about type, this approach might be faster. * `hasOwnProperty` is slower than `in` but can be faster with modern JavaScript engines that optimize this method. It's also safer because it specifically checks for existing properties without considering inherited ones. * `! obj[k];` is similar to `typeof` and negation in that it uses direct property access followed by logical negation. However, since the variable is already known to be an object property (thanks to being stored in `obj`), this approach avoids some of the overhead. In terms of special JavaScript features or syntax, none are explicitly used beyond the standard operators (`in`, `typeof`) and logical operations. When it comes to alternative approaches, other methods for checking if a property exists include: * Using a `for...in` loop to iterate over the object's properties * Using the `Object.prototype.hasOwnProperty.call()` method (available since ECMAScript 2015) * Using modern JavaScript engines' built-in optimization techniques, such as `Object.hasOwn()` However, these alternatives might not provide significant performance gains compared to the methods being tested here. Overall, this benchmark aims to compare the performance of different approaches for checking if a property exists in an object. The results indicate that `in` is generally the fastest, followed by `hasOwnProperty`, while `typeof` and negation and `! obj[k];` are less efficient due to their limitations and potential performance issues.
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