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The Mechanics Behind JavaScript’s typeof and instanceof
- typeof in JavaScript is a method to determine the type of a given value, but it has some quirks like returning 'object' for null and arrays.
- It categorizes values into only eight possible results, such as 'number', 'boolean', and 'function'.
- Checking for null with typeof can be misleading, and it's advised to use strict equality checks for null values.
- typeof considers arrays as objects in JavaScript because arrays are a special type of object with additional behaviors.
- To specifically check if a value is an array, Array.isArray() should be used.
- Functions are treated uniquely by typeof, returning 'function' as the type, even though functions are technically objects.
- Instances of functions like async generator functions or callable Proxy objects are also categorized as 'function' by typeof.
- For primitive types, typeof works as expected, providing a straightforward way to identify basic values.
- Boxed versions of primitives, created by wrapper constructors, may lead to confusion as typeof returns 'object' for them.
- The instanceof operator in JavaScript examines the connection between an object and its prototype chain, focusing on inheritance rather than creation.
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