对JavaScript中的构造函数感到困惑

Question

Please excuse me if I am missing anything important or even silly. I'm trying to print the constructor's name from objects. I followed two approaches.

First approach's code is below,

var CF = function () {
   p1 = "";
   p2 = "";
}
var cf1 = new CF();
cf1.constructor.name

Output :

""

second code,

function CF() {
   p1 = "";
   p2 = "";
}
var cf1 = new CF();
console.log(cf1.constructor.name);

Output :

CF 

I guess you have undertood what I wanted to say. The first CF 's objects constructor name is "" where as second ones output is CF .

I tried to know the differnce like below

var CF = function() { }
typeof CF;
function CF() { };
typeof CF

But no luck they both output

"function"

Why is that behavior with first approach? What is the difference?

(I'm using chrome console)

Answer 1

The first constructor function is an anonymous function meaning it has no name. The second constructor function has a name which allows its constructor to be printed.

Answer 2

In the first approach you just create an object named CF that contains an unnamed function that is a constructor for a class which is unknown until that point.

In the second code you write the constructor for the class in a function named CF and then use that constructor to create an instance of your class in the object named cf1.

I hope you understand what I'm trying to say, basically your first constructor has no name.

Answer 3

function CF() { }; is shorthand for var CF = function() { } , so typically they are the same.

That being said, function CF() { }; gives you some benefit in debugging in node, since it allows node to give more precise feedback on what/where went wrong.