How to view constructor properties of a function in javascript?

Question

for example, I create a constructor function called Test,

         function Test(a,b)
         {
               this.a = a;
               this.b = b;
               var test = "test";
         }

When I attempt to view the properties of the Test constructor in firefox debug mode, I don't see these properties (a, b, and test) I define. Why?

The constructor is just an ordinary function. The properties are in the objects that you create with it. — Barmar
– Barmar, Commented Jun 29, 2018 at 1:04
True, I did see the properties through the object but how can I view them from the constructor function? — Nora
– Nora, Commented Jun 29, 2018 at 1:09
You can't, they're not part of the constructor function. The constructor function just executes that as code. — Barmar
– Barmar, Commented Jun 29, 2018 at 1:12

Barmar · Accepted Answer · 2018-06-29 01:14:10Z

1

a and b are not properties of the constructor. When you create an object using the constructor, the object will get those properties as a result of the assignments. But as far as the constructor itself is concerned, those are just ordinary lines of code, there's nothing special that makes them act as properties.

var t = new Test(1, 2);

If you view t you will see the a and b properties.

test is not a property at all, it's just a local variable inside the constructor. The only way to see it is to set a breakpiont in the constructor and examine the local variables. Variables are not part of a Function object.

edited Jun 29, 2018 at 1:14

answered Jun 29, 2018 at 1:08

Barmar

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