javascript - How do I add prototype-like properties to an existing object? -

i start off simple object like:

var person = { name: 'joe', age: 21 }; 

i want add method object without method showing when use hasownproperty. example, let's create birthday method increments person's age.

var birthday = function() { this.age++; }; 

how add person object if say:

for(var in person) {   console.log(i); } 

i get:

name: 'joe' age: 21 birthday: function() { ... } 

but if say:

for(var in person) {   if(person.hasownproperty(i)) {     console.log(i, person[i]);   } } 

i get:

name: 'joe' age: 21 

var person = { name: 'joe', age: 21 };    object.defineproperty(person, 'birthday', {    enumerable: false,    configurable: false,    writable: false,    value: function() { this.age++; }  });    function showperson() {    for(var in person) {      if(person.hasownproperty(i)) {        console.log(i, person[i]);      }    }  }    showperson();  person.birthday();  showperson();

if iterating methods without hasownproperty important,. following idea might work..

var person = { name: 'joe', age: 21 };    var extend = {    birthday: function () { this.age ++ }  }    var person = object.assign(    object.create(extend),    person);        function showperson() {    for(var in person) {      if(person.hasownproperty(i)) {        console.log(i, person[i]);      }    }  }    function showpersonfull() {    for(var in person) {      console.log(i, person[i]);    }  }    showperson();  person.birthday();    showpersonfull();

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