What are JavaScript properties and their connection to objects?

Properties

In JavaScript, properties are the values associated with an object. Properties are an object’s characteristics or attributes. They can store data types, including primitive values (such as booleans, numbers, and strings) or references to other objects.

Connection to objects

In JavaScript, objects are collections of key-value pairs, where each key is a property name, and each value is the respective property’s value.

Create an object

We can create an object using an object initializerAn object initializer is a comma-delimited list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}). as follows:

let objectName = {
    property1: value1,    // Property name can be an identifier
    2: value2,            // Property name can be a number
    "property n": value3, // Property name can be a string
};
Syntax for creating an object

Access properties of an object

Accessing properties in JavaScript is straightforward. We can use either dot notation or bracket notation to access the values associated with object properties.

Dot notation

We use the dot notation to access a property of an object, as shown below:

let author = {
  name: 'John',
  age: 33,
};
// Let's access the properties of an object
console.log(author.name);
console.log(author.age);

In the given code:

  • Lines 1–4: We create an author object with two properties: name and age.

  • Lines 6–7: We use the dot notation to access the name and age properties of the author’s object.

Bracket notation

Another way to access a property of an object is by using the bracket notation, as shown below:

let author = {
  name: 'John',
  age: 33,
};
// Let's access a property of an object
console.log(author['name']);

In the given code:

  • Line 6: We use the bracket notation to access the 'name' property of the author’s object.

Add and modify a property

We can create a new property, or we can assign a new value to an existing property on the object, as shown below:

let author = {
  name: 'John',
  age: 33,
};
// Let's create a new property
author.job = 'JavaScript Expert';
console.log(author.job);
// Let's modify an existing property
author.age = 31;
console.log(author.age);

In the give code:

  • Line 6: We create a new property (i.e., job) for the author’s object.

  • Line 9: We modify the age property of the author’s object.

Delete a property

We can also delete a specific property of an object as follows:

let author = {
  name: 'John',
  age: 33,
};
// Let's delete a property
delete author.age;
console.log(author.age);

In the give code:

  • Line 9: We delete the age property of the author’s object using the delete operator.

Note: After deleting the age property of the author’s object, the author.age will return “undefined”.

Conclusion

In summary, JavaScript properties are the key-value pairs associated with an object. They can be accessed, added, modified, or deleted dynamically.

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