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.

Its better to use 'for of' instead of 'for in': https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Statements/for...of — Teemoh, Apr 22 '18 at 11:50
Just use `for (var obj of persons) { console.log(obj.fullName); }` instead. — Bergi, Apr 22 '18 at 12:49

Mamun · Accepted Answer · 2018-04-22T11:49:28.357

0

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);

edited Apr 22 '18 at 11:49

answered Apr 22 '18 at 11:47

Mamun

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I wouldn't go for a 'for in-loop' here. Instead I would use 'for of', which loops directly over the values instead of the keys. Check https://stackoverflow.com/questions/500504/why-is-using-for-in-with-array-iteration-a-bad-idea?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa for the problem. – Teemoh Apr 22 '18 at 11:49
@Teemoh, but OP mentioned in the question that he want solution with `for in` – Mamun Apr 22 '18 at 11:51
Yeah i know, I just wrote the comment also at the question – Teemoh Apr 22 '18 at 11:51
Thanks to all! That’s perfect. Did you think it is necessary the array with the objects? Can I do this only with the variables? Can't I, isn't it? @Mamun – jaumeserr Apr 22 '18 at 11:54
[Don't use `for…in` enumerations on arrays!](https://stackoverflow.com/q/500504/1048572) – Bergi Apr 22 '18 at 12:48

for...in key values instanced object instead forEach in JavaScript

1 Answers1