为什么不将“function”视为javascript中的数据类型？

Question

The datatypes listed in MSDN for javascript are Number, String, Boolean, Object, Array, Null, Undefined. However, when you do typeof function , its type is function.

Why is this the case, and what's the definition of datatype?

Answer 1

Functions are just Objects in JavaScript. But the difference lies in an internal property called [[Call]] that differentiates them from normal Objects. When typeof is used against an Object, and if it finds the [[Call]] property, then it returns the String "function".

This behavior can be found in the ECMA Specification for typeof .