Why in JavaScript class A instanceof Function, but typeof class A is not an object?

Question

When we say "instance of", we assume that we are dealing with an object. Why JavaScript's operator instanceof returns true when we ask (class A { }) instanceof Function , but typeof (class A { }) == "function" ? Why not object ?

Answer 1

Why JavaScript's operator instanceof returns true when we ask (class A { }) instanceof Function

class es are just syntactic sugar for constructor functions. Ie the evaluation of class A {} produces a function.

The following two examples are (more or less) equivalent, ie they produce the same result/value:

// class
class A {
  constructor() {
    this.foo = 42;
  }

  bar() {
    console.log(this.foo);
  }
}

// constructor function
function A() {
  this.foo = 42;
}

A.prototype.bar = function() {
  console.log(this.foo);
}

Everything that is not a primitive value (string, number, boolean, null, undefined, symbol) is an object in JavaScript. Functions are objects too, with special internal properties that makes them callable (and/or constructable ).

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Why not object?

typeof returns the string "function" for function values because that's how it is defined in the specification.