Initializing key and value pairs Javascript Object

Question

I've seen developers declare an empty object and later assign properties and values to it but I mostly create an object and initialize the properties and values. Example

const data = {}
data.name = "John Doe";
data.age = 60;

What I mostly do is :

const data = {
name: "John Doe",
age: 60
}

I will like to know the difference between the two and why will you pick one over the other. Thanks

There isn't any difference in the result. I think some people whom have come from other languages than JavaScript tend to use paradigms that apply to their learned language but don't necessarily apply to JavaScript. — Emiel Zuurbier
– Emiel Zuurbier, Commented Jul 23, 2021 at 20:46
Use the second (albeit with indentation) - it's less to type, does not repeat the name data, and makes the structure of the object immediately visible. — Bergi
– Bergi, Commented Jul 24, 2021 at 13:59

Ravi · Accepted Answer · 2021-07-23 20:40:52Z

2

Technically there is not much difference if you are declaring and assigning values immediately. But if you have to populate conditionally then the first option is better. However you can also conditionally update a populated object.

answered Jul 23, 2021 at 20:40

Ravi

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Comments

Danial · Accepted Answer · 2021-07-24 07:41:44Z

Declaring objects in Javascript is easiest than other programming languages. For example in C# (or Java), first you must declare structure of object, then you create an instance of that.

using System;

namespace Example
{
    public struct Person
    {
        public string Name;
        public int Age;
        public Person(string name, int age)
        {
            Name = name;
            Age = age;
        }
    }

    public class Application
    {
        static void Main()
        {
            Person p1 = new Person("John Doe", 60);
            Console.WriteLine("p1 Name = {0} Age = {1}", p1.Name, p1.Age);
        }
    }
}

But in Javascript you can declare structure of object or not. Even you can modify that structure after declaring. That's amazing (maybe not). This feature of Javascript can produce many problems.

So, there is no difference. But if you declare the structure, code will be more cleaner.

For more information:

https://javascript.info/object

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