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isFunction vs typeof function 5
(version: 0)
isFunction vs typeof function
Comparing performance of:
isFunction vs typeof function vs instanceof
Created:
7 years ago
by:
Guest
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HTML Preparation code:
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.core.js"></script>
Tests:
isFunction
function onClose () { console.log('hey') } var isfunc = _.isFunction(onClose);
typeof function
function onClose () { console.log('hey') } var isfunc = typeof onClose === 'function';
instanceof
function onClose () { console.log('hey') } var isfunc = onClose instanceof Function;
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (3)
Previous results
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Test case name
Result
isFunction
typeof function
instanceof
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's dive into the details of this benchmark. **Benchmark Overview** The test compares three different approaches to check if a function exists in JavaScript: 1. `isFunction` (from Lodash library) 2. `typeof function` 3. `instanceof Function` Each approach has its pros and cons, which I'll explain below. **1. `isFunction` (Lodash library)** Pros: * Specifically designed for checking function existence * Can handle complex function types (e.g., arrow functions, generators, etc.) * Part of a widely-used and well-maintained library (Lodash) Cons: * Requires including the Lodash library in the test environment * May introduce additional overhead due to the library's size and complexity **2. `typeof function`** Pros: * Lightweight and fast, as it only checks the type of the variable * Native JavaScript functionality, no external dependencies required Cons: * Only works for functions that are explicitly declared as such (e.g., `var func = function() { ... };`) * Can be misleading if the variable is a complex data structure or an object with a function property * Does not account for function expressions (e.g., `var func = () => { ... };`) **3. `instanceof Function`** Pros: * Similar to `typeof function`, but more explicit and intuitive * Works for functions that are explicitly declared as such Cons: * Requires a specific type check (`Function`) which might not cover all cases (e.g., constructor functions, etc.) * Can be slower due to the additional type check **Library: Lodash** Lodash is a popular JavaScript library that provides various utility functions. In this case, `_.isFunction` is used to check if a variable is a function. Lodash's purpose is to provide a set of functional programming helpers and utilities for tasks such as data manipulation, array and object operations, and more. **Special JS feature or syntax** There are no special JavaScript features or syntax used in this benchmark that would require explanation beyond the existing content. **Alternatives** Other alternatives to these approaches could include: * Using a custom implementation of a function existence check * Leveraging modern JavaScript features like `Function.isConstructable()` (if supported) for more explicit checks * Utilizing third-party libraries or frameworks with built-in function existence checking functionality However, it's worth noting that Lodash's `_.isFunction` is a widely-used and well-established solution for this specific problem, making it a reasonable choice for benchmarking purposes.
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