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JavaScript JavaScript Loops, Arrays and Objects Tracking Data Using Objects Using `for in` to Loop Through an Object's Properties

Posted by Iliya Narsiya
Iliya Narsiya
2,054 Points

How enumerate properties the object in which have another one object?

How enumerate properties the object in which have another one object? Please, with comment on code.

For example:

var person = {

name:"Sarah", age: 35, country: "USA",

size: { top: 90, middle: 60, bottom: 90 }

}

2 Answers

Justin Horner
STAFF
Justin Horner
Treehouse Guest Teacher
Justin Horner
Justin Horner
Treehouse Guest Teacher

Hello Iliya,

In order to loop through inner objects you would use a for...in loop on the property of the object like this.

var person = {
    name:"Sarah", age: 35, country: "USA",
    size: 
    { 
        top: 90, 
        middle: 60, 
        bottom: 90 
    }
}

for (var key in person.size) {
    console.log('Key: ', key, ' Value: ', person.size[key]);
}

I hope this helps.

Iliya Narsiya
Iliya Narsiya
2,054 Points

var fruits = { 'apple': { 'color': 'green', 'sort': 'Granny Smith', 'Country': 'Russia', 'price': 68 }, 'orange': { 'color': 'orange', 'sort': 'Valencia', 'country': 'Spain', 'price': 100.99 }, 'pear': { 'color': 'red', 'sort': 'Conference', 'country': 'Cyprus', 'price': 120.59 }, 'netto' : 125600 // not is object };

I was meant, how print out all properties, that be to look like :

apple : color = green apple : sort = Granny Smith apple : Country = Russia apple : price = 68 orange : color = orange orange : sort = Valencia orange : country = Spain orange : price = 100.99 pear : color = red pear : sort = Conference pear : country = Cyprus pear : price = 120.59 netto = 125600

Justin Horner
STAFF
Justin Horner
Treehouse Guest Teacher
Justin Horner
Justin Horner
Treehouse Guest Teacher

Hello Iliya,

Sorry for the misunderstanding. If you want to loop through every key value pair in an object, you can use the typeof operator to discover which properties are objects. Once you know that, you can use the function recursively to print the properties of the inner object and so forth.

Here's an example of how you could accomplish this with your object example.

function printObjectDetails(obj) {
    for (var key in obj) {
            console.log('Key: ', key, ' Value: ', obj[key]);

            if (typeof obj[key] === 'object') {
                printObjectDetails(obj[key]);   
            }
      }   
}

var person = {
    name:"Sarah", 
    age: 35,
    country: "USA",
    size: 
    { 
        top: 90, 
        middle: 60, 
        bottom: 90 
    }
}

printObjectDetails(person);

I hope this helps.

Iliya Narsiya
Iliya Narsiya
2,054 Points

Thank you, for you try help me!

I confused, that function print out - Value: [object Object] instead - size Key: top Value: 90Key: middle Value: 60Key: bottom Value: 90

Key: name Value: SarahKey: age Value: 35Key: country Value: USAKey: size Value: [object Object]Key: top Value: 90Key: middle Value: 60Key: bottom Value: 90