Is "function" a JavaScript type?
For example:
console.log(typeof alert) // returns function
Which suggests that "function" is indeed a type
However, in this ECMAscript documentation it says:
The ECMAScript language types are Undefined, Null, Boolean, String, Symbol, Number, BigInt, and Object”.
Could someone explain this to me?
Thanks in advance :)
The behaviour of the typeof operator is documented in section 12.5.5, which has a table that answers your question.
It says (paraphrased):
typeof val:
val is an Object which implements the [[Call]] interface then typeof returns the string 'function'val is an Object which does not implement [[Call]] then typeof returns the string 'object'.Thus, function is not a separate ECMAScript type, but is actually a specialization of the Object-type.
Do note that the information in the ECMAScript specification is very technical and narrowly specific and is intended primarily for implementors of ECMAScript engines and tooling - and while it is useful for developers using JS as a language, it is not intended to be beginner-friendly or serve as an introduction to the language - or to explain fundamentals.
The precise definition of a "function object" is explained in 6.1.7.2.
Functionas a separate ECMAScript type - that page says it's a "structural type" which is not the same thing as a fundamental ECMAScript type.