Javascript custom object is shared

Question

I am trying to maximize the reuse of some code. In my custom javascript object (I just use PhoneNumber for an example), I set up a prototype function like this:

var Map = {
    write: function() {
        alert('My object is ' +this);
    }
};

function PhoneNumber(number) {
    this.number = number;
}

PhoneNumber.prototype = Map;

//I can call the write function like so
var phoneObject = new PhoneNumber('1234567894');
phoneObject.write(); //ALERT My Object is Object{number:'1234567894'}

Everything works fine, except for some reason it turns my Phone Number object into a shared object instead of saving its PhoneNumber constructor. If I really place the write function inside a prototype of objects like this, it works great.

function PhoneNumber(number) {
    this.number = number;
}

PhoneNumber.prototype.write = function() {
    alert('My object is ' +this);
}

var phoneObject = new PhoneNumber('1234567894');
phoneObject.write(); //ALERT My object is PhoneNumber{number:'1234567894'}

, , . ? -, Map , , Map . ?

Answer 1

PhoneNumber.prototype.constructor

PhoneNumber.prototype = Map,

PhoneNumber.prototype = Map;
PhoneNumber.prototype.constructor = PhoneNumber;

, , Map.constructor = PhoneNumber, , Map . , PhoneNumber

PhoneNumber.prototype = Object.create(Map, {
  constructor: { value: PhoneNumber }
});

Answer 2

My object is [object Object] Firefox.

, :

JavaScript?

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Answer 3

function PhoneNumber(number) {
    this.number = number;
}
var Map={
    write:function(){        
        console.log('My object is ' +this.number);
    }
}
PhoneNumber.prototype.write = Map.write;

var phoneObject = new PhoneNumber(1234567894);
phoneObject.write();

. , Map, .

Answer 4

, PhoneNumber toString. :

var Map = {
    write: function() {
        alert('My object is ' +this);
    }
};

function PhoneNumber(number) {
    this.number = number;
    this.toString = function(){return "PhoneNumber"}
}

PhoneNumber.prototype = Map;

//I can call the write function like so
var phoneObject = new PhoneNumber('1234567894');
phoneObject.write(); //ALERT My Object is Object{number:'1234567894'}