for…in key values instanced object instead forEach in JavaScript

Question

Is there any way to do a for...in key values instanced object instead forEach ? With forEach is easy for me but I'm looking for to do it with for...in.

I made this with for each:

function Person(fullName, gender, city) {
    this.fullName = fullName;
    this.gender = gender;
    this.city = city;
}

var person01 = new Person("Nancy", "Female", "Los Angeles");
var person02 = new Person("James", "Male", "New York");
var person03 = new Person("Lucia", "Female", "Santa Barbara");


//To do the loop
var persons = [
    {fullName: "Nancy", gender: "Female", city: "Los Angeles"},
    {fullName: "James", gender: "Male", city: "New York"},
    {fullName: "Lucia", gender: "Female", city: "Santa Barbara"},
]

function listNames(myObject) {

    persons.forEach(function(obj) {
        console.log(obj.fullName);  
    });
}

listNames(persons);
//Nancy, James, Lucia

This way works, but I need to understand how its works the for in.

Answer 1

Try the following:

for(var key in myObject){
  console.log(myObject[key].fullName);
}

Working Example:

 function Person(fullName, gender, city) { this.fullName = fullName; this.gender = gender; this.city = city; } var person01 = new Person("Nancy", "Female", "Los Angeles"); var person02 = new Person("James", "Male", "New York"); var person03 = new Person("Lucia", "Female", "Santa Barbara"); //To do the loop var persons = [ {fullName: "Nancy", gender: "Female", city: "Los Angeles"}, {fullName: "James", gender: "Male", city: "New York"}, {fullName: "Lucia", gender: "Female", city: "Santa Barbara"}, ] function listNames(myObject) { for(var key in myObject){ console.log(myObject[key].fullName); } } listNames(persons);