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JavaScript Object initializer
  • Last Updated : 15 Oct, 2020

Objects in JavaScript can be compared to real-life objects. They have properties and methods attached to them and properties are in the form of key-value pairs. Let us understand this with an example. In the real-world, a motorcycle is an object and it has properties like name, color, price, etc. It has some methods attached to it like start, brake, stop, etc. All motorcycles will have similar properties but the values will be different. This same concept is applied in programming and is known as Object Oriented Programming.

JavaScript objects can be initialized in various ways which are as follows.

  1. Using object literals
  2. Using new Object() method
  3. Using Object.create() method
  4. Using constructor functions

Let us understand all the methods –

Using Object Literals:
Syntax:

var obj = { name: "value", .... }

Properties of JavaScript object can be accessed using a dot notation or bracket notation. For Example, obj.name or obj[‘name’] will give us the value.



Example:

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var person = {
  name: "Sarah",
  age: 20,
  gender: "female"
};
console.log(person);
console.log(person.name + " is a " + person.age +
           year old " + person.gender); 
console.log(person.name + " is a " + person.age + "
           year old " + person["gender"]); 

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Output:


Using new Object() method:

Syntax:

var obj = new Object();
    obj.name = "value";

or

obj["name"] = "value";

The new Object() method will make a new JavaScript object whose properties can be initialized using dot or bracket notation.

Example:



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var Person = new Object();
Person.name = "Sarah";
Person['age'] = 20;
Person.gender = "female";
  
console.log(Person);
console.log(Person.name + " is a " + Person.age +
           " year old " + Person.gender); 
console.log(Person.name + " is a " + Person.age + 
          " year old " + Person["gender"]); 

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Output:

Using Object.create() method:

Syntax:

var Obj = Object.create({});
Obj.name = "value";

or

Obj["name"] = "value";

The Object.create() method will make a new JavaScript Object whose properties can be initialized using dot or bracket notation.

Example:

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var Person = Object.create({})
Person.name = "Sarah";
Person["age"] = 20;
Person.gender = "female";
  
console.log(Person);
console.log(Person.name + " is a " + Person.age +
           " year old " + Person.gender); 
console.log(Person.name + " is a " + Person.age + 
          " year old " + Person["gender"]); 

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Output:




Using Constructor functions:

Syntax:

function Obj(name) {
   this.name = name;
 }
 var myobj = new Obj("my name");

In this method, constructor function is used to define the object and this is used to assign value to the properties. An instance of the object is created using new keyword.

Example:

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function Person(name, age, gender) {
    this.name = name;
    this.age = age;
    this.gender = gender;
 }
   
 var personOne = new Person("Sarah", 20, "gender");
  
console.log(personOne);
console.log(personOne.name + " is a " + personOne.age +
            " year old " + personOne.gender); 
console.log(personOne.name + " is a " + personOne.age +
            " year old " + personOne["gender"]); 

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Output:

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