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Is a instanceof b exactly equivalent to a.constructor === b? If not, what's the difference between the two?
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typeof: Per the MDN docmentation, typeof is a unary operator that returns a string indicating the type of the unevaluated operand. instanceof: is a binary operator, accepting an object and a constructor. It returns a boolean indicating whether or not the object has the given constructor in its prototype chain.
The instanceof operator tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an object. The return value is a boolean value. Its behavior can be customized with Symbol.
The instanceof operator in JavaScript is used to check the type of an object at run time. It returns a boolean value if true then it indicates that the object is an instance of a particular class and if false then it is not.
The java “instanceof” operator is used to test whether the object is an instance of the specified type (class or subclass or interface). It is also known as type comparison operator because it compares the instance with type. It returns either true or false.
No.
instanceof also checks for "inherited" constructors.
For more information, see the spec. (here and here)
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