Javascript Object Type

Introduction

Instances of Object are used to store data.

There are two ways to create an instance of Object.

The first is to use the new operator with the Object constructor: 

let person = new Object(); 
person.name = "HTML"; 
person.age = 29;

The other way is to use object literal notation.

For example, the following defines the same person object from the previous example using object literal notation: 

let person = {
    name: "HTML",
    age: 29
};

Property names can be specified as strings or numbers when using object literal notation: 

let person = {
    "name": "HTML",
    "age": 29,
    5: true
};

It's also possible to create an object with only the default properties and methods using object literal notation: 

let person = {}; // same as new Object() 
person.name = "HTML";
person.age = 29;

The object literals is a preferred way of passing a large number of optional arguments to a function: 

function displayInfo(args) {
    let output = "";

    if (typeof args.name == "string") {
        output += "Name: " + args.name + "\n";
    }//from w  w  w .ja  v  a  2  s. com

    if (typeof args.age == "number") {
        output += "Age: " + args.age + "\n";
    }

    console.log(output);
}

displayInfo({
    name: "HTML",
    age: 29
});

displayInfo({
    name: "Javascript"
});

We can access properties via bracket notation. 

console.log(person["name"]);  // "HTML" 
console.log(person.name);     // "HTML"

The bracket notation allows you to use variables for property access: 

let propertyName = "name"; 
console.log(person[propertyName]);  // "HTML"

You can use bracket notation when the property name contains characters: 

person["first name"] = "HTML";



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