I am not able to understand when to use proto and prototype

Question

 let person ={
        name:"ayush",
        class:12
    }
function man(){
        
    }

In case of function man if I write man.proto it gives ƒ () { [native code] }

when I write man.prototype I am getting {constructor: ƒ}

but in case of object person if i wirte person.proto it gives me {constructor: ƒ, defineGetter: ƒ, defineSetter: ƒ, hasOwnProperty: ƒ, lookupGetter: ƒ, …}

when I write person.prototype it gives undefined

Why results varries in case of object and function?

You might be confused about the fundamentals. The fundamental rule is *the prototype of object `new f()` is `f.prototype`.* Does that make sense to you? If yes, then you can figure out the answers to your own questions; drawing a diagram where boxes are objects and labeled arrows are properties of the object will help. If no, then work on understanding the fundamentals. — Eric Lippert, May 05 '21 at 16:58
Once you get that fundamental rule in your head then your observations start making sense. Why is `person.prototype` undefined? Because there is no such thing as `new person()`. If `person` were a function then it would need a `.prototype` property so that `new person()`'s prototype is `person.prototype`. But `person` is not a function. Does that make sense to you? If not, can you ask a more focused question that would unblock you? — Eric Lippert, May 05 '21 at 17:03
The other thing you need to know to understand what is going on is: `person` behaves as though it was a `new Object()`, so its prototype is `Object.prototype`. `man` behaves as though it was a `new Function()` so its prototype is `Function.prototype`. That all follows from the fundamental rule. — Eric Lippert, May 05 '21 at 17:06
Can you tell me any source from which I can learn prototype basics? because I am new to programming and today only I started prototype concept after completing basics of java script — , May 05 '21 at 17:29

score 0 · Answer 1 · edited May 05 '21 at 17:13

You should never use the .__proto__ property, it still exists for backwards compatibility but is considered deprecated in favor of Object.getPrototypeOf().

Now to explain what you observed:

let person = {
    name: "ayush",
    class: 12
}

function man() {}

console.log(Object.getPrototypeOf(person));
// Object.prototype because person is an instance of Object

console.log(person.prototype);
// undefined because an object has no prototype property, it's not a constructor function

console.log(Object.getPrototypeOf(man));
// Function.prototype

console.log(man.prototype);
// object. man.prototype is actually an empty object to be filled with
// methods for future use as a constructor function with the new operator

I am not able to understand when to use __proto__ and prototype

1 Answers1

I am not able to understand when to use proto and prototype