Javascript中的“功能对象”一词实际上是什么意思？

Question

After reading a lot, I still don't quite understand the term function objects in JS. From what I have read, following are my interpretations. Please correct if I'm wrong.

function myfunc(x){
 return x;
}

Interpretation : myfunc is a function object auto created by JS interpreter internally whenever a new function like myfunc is declared as shown above.

var myObj = new myfunc();
var mynewObj = new myfunc();

Interpretation : myObj and mynewObj are instances(objects) of myfunc thus can be said to be a function objects

Are my interpretations correct. Any other examples of function objects?

thanks

bt

Answer 1

Interpretation: myfunc is a function object auto created by JS interpreter internally whenever a new function like myfunc is declared as shown above.

Almost, but not quite. myfunc is an identifer that refers to (points to) a function created by the JavaScript engine. ¹ That function is an object, because all functions are objects in JavaScript. You could call it a "function object" if you like; most people would just call it a "function." (In JavaScript "function" and "function object" are synonyms.)

 var myObj = new myfunc(); var mynewObj = new myfunc(); 

Interpretation: myObj and mynewObj are instances(objects) of myfunc thus can be said to be a function objects

No, they're not function objects. They're just objects. They are indeed instanceof myfunc which means that the object myfunc.prototype points to is in their prototype chain, but it's not correct at all to call them "function objects" because they aren't functions.

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¹ "JavaScript engine" - This is the term I use in preference to "JavaScript interpreter" because any modern JavaScript engine is a just-in-time-compiler plus runtime environment, not an interpreter. It's a subtle distinction.

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In a comment, Jamie Dixon mentions the Function function. It's just a function that creates functions based on source code strings. There are virtually no use cases for it in modern JavaScript (just as there are virtually no use cases for eval in modern JavaScript).