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If null is a primitive, why does typeof(null) return "object"?

Because the spec says so.

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

 

1. Let val be the result of evaluating UnaryExpression.
2. If Type(val) is Reference, then
      a. If IsUnresolvableReference(val) is true, return "undefined".
      b. Let val be GetValue(val).
3. Return a String determined by Type(val) according to Table 20.

If null is a primitive, why does typeof(null) return "object"?

Because the spec says so.

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

1. Let val be the result of evaluating UnaryExpression.
2. If Type(val) is Reference, then
      a. If IsUnresolvableReference(val) is true, return "undefined".
      b. Let val be GetValue(val).
3. Return a String determined by Type(val) according to Table 20.

If null is a primitive, why does typeof(null) return "object"?

Because the spec says so.

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

1. Let val be the result of evaluating UnaryExpression.
2. If Type(val) is Reference, then
     a. If IsUnresolvableReference(val) is true, return "undefined".
     b. Let val be GetValue(val).
3. Return a String determined by Type(val) according to Table 20.

If null is a primitive, why does typeof(null) return "object"?

Because the spec says so.

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

1. Let val be the result of evaluating UnaryExpression.
2. If Type(val) is Reference, then
        a. If IsUnresolvableReference(val) is true, return "undefined".
        b. Let val be GetValue(val).
3. Return a String determined by Type(val) according to Table 20.

If null is a primitive, why does typeof(null) return "object"?

Because the spec says so.

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

1. Let val be the result of evaluating UnaryExpression.
2. If Type(val) is Reference, then
    a. If IsUnresolvableReference(val) is true, return "undefined".
    b. Let val be GetValue(val).
3. Return a String determined by Type(val) according to Table 20.

If null is a primitive, why does typeof(null) return "object"?

Because the spec says so.

11.4.3 The typeof Operator

The production UnaryExpression : typeof UnaryExpression is evaluated as follows:

1. Let val be the result of evaluating UnaryExpression.
2. If Type(val) is Reference, then
    a. If IsUnresolvableReference(val) is true, return "undefined".
    b. Let val be GetValue(val).
3. Return a String determined by Type(val) according to Table 20.