Objects in JavaScript

OBJECTS IN JAVASCRIPT

In JavaScript, an object is an unordered collection of key-value pairs. Each key value pair is called a property.
Key of a property can be a string and the value of a property can be any value, e.g. number, function or array.
JavaScript provides (many) exact number ways to create an object. Most commonly used is to use the object literal notation.

Literal notation

The following is an example of creating an object student using literal notation;

How to Create Objects in JavaScript

let student = {};

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To create an object with properties, you use key-value in curly braces.
For example;

let studentDetails= {firstname} ’Gladwin’
let student=new object
Console.log (studentDetails);

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The Student object has one property: firstName.
Object Constructor

How to access properties in Objects

The dot (.) notation

You can access a property in javascript objects by using a dot sign
syntax

objectName.Propety

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The following illustrates how to use dot notation to access a property of an object.
objectName . propertyName
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The following illustrates how to access the value of an object’s property using bracket/array-like notation.

objectName[ ‘propertyName’]

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For example;

let student = {
firstName: ‘Gladwin’
console.log (student [firstName]);

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Modifying the value of a property
To change the value of a property, you use the assignment operator (=).
For example:

let student ={
firstName: ‘Gladwin’
student.firstName= ‘Gladwin’;
console.log (student);

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Adding a new property to an object

The following statement adds the adm no. property to the student object and assign 32919 to it;

student.adm no =32919;
console.log (student);

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Deleting a property of an object

To delete a property in an object, you use the delete operator.

delete objectName. propertyName;

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The following example removes the adm no. property from the student object.

delete  student.adm no.;

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Checking if a property exists

To check if a property exists in an object, you use the in operator;

propertyName in objectName

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The in operator returns true if the propertyName exists in objectName.

The following example creates a student object and uses the in operator to check if studentId property exists in the object.

let student= {
firstName: ‘Gladwin’
studentId: 6
};
console.log (studentId in student);

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