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JavaScript•Objects, Classes, and Advanced Patterns

JavaScript Object Properties

Flash cards

Review the key moves

1/4

Core idea

What is the main idea behind JavaScript Object Properties?

Lesson checks

Practice each idea before moving on

Short Mimo-style checks built from this lesson's code, terms, and sequence.

1Quick choice

Which statement best captures the main point of this lesson?

2Fill blank

Complete the missing token from the example code.

___.age = 10;

3Order

Put the learning moves in the order that makes the concept easiest to apply.

Changing Properties

Accessing JavaScript Properties

Properties are key:value Pairs

A JavaScript object is a collection of properties

Properties can be changed , added , and deleted .

Accessing JavaScript Properties

You can access object properties in these ways:

Dot notation
Bracket notation
Expression

Changing Properties

You can change the value of a property:

person.age = 10;

Adding New Properties

You can add a new property by simply giving it a value:

person.nationality = "English";

Deleting Properties

The delete keyword deletes a property from an object:

Examples

const person = {
  firstName: "John", lastName: "Doe", age: 50, };
delete person.age;

The delete keyword deletes both the value and the property .

After deleting, the property is removed. Accessing it will return undefined .

Check if a Property Exists

Use the in operator to check if a property exists in an object:

Example

const person = {
  firstName: "John", lastName: "Doe"
};
let result = ("firstName" in person);

Nested Objects

Property values in an object can be other objects:

Example

myObj = {
 name:"John",
 age:30,
 myCars: {
 car1:"Ford",
 car2:"BMW",
 car3:"Fiat"
 }
}

You can access nested objects using the dot notation or the bracket notation:

myObj.myCars.car2;

Summary

Object properties are key:value pairs
Access properties with dot notation or bracket notation
Add, change, and delete properties using assignment and delete
Use the in operator to check if a property exists

JavaScript Object Properties

Flash cards

Review the key moves

1/4

Core idea

What is the main idea behind JavaScript Object Properties?

Lesson checks

Practice each idea before moving on

Short Mimo-style checks built from this lesson's code, terms, and sequence.

1Quick choice

Which statement best captures the main point of this lesson?

2Fill blank

Complete the missing token from the example code.

___.age = 10;

3Order

Put the learning moves in the order that makes the concept easiest to apply.

Changing Properties

Accessing JavaScript Properties

Properties are key:value Pairs

A JavaScript object is a collection of properties

Properties can be changed , added , and deleted .

Accessing JavaScript Properties

You can access object properties in these ways:

Dot notation
Bracket notation
Expression

Changing Properties

You can change the value of a property:

person.age = 10;

Adding New Properties

You can add a new property by simply giving it a value:

person.nationality = "English";

Deleting Properties

The delete keyword deletes a property from an object:

Examples

const person = {
  firstName: "John", lastName: "Doe", age: 50, };
delete person.age;

The delete keyword deletes both the value and the property .

After deleting, the property is removed. Accessing it will return undefined .

Check if a Property Exists

Use the in operator to check if a property exists in an object:

Example

const person = {
  firstName: "John", lastName: "Doe"
};
let result = ("firstName" in person);

Nested Objects

Property values in an object can be other objects:

Example

myObj = {
 name:"John",
 age:30,
 myCars: {
 car1:"Ford",
 car2:"BMW",
 car3:"Fiat"
 }
}

You can access nested objects using the dot notation or the bracket notation:

myObj.myCars.car2;

Summary

Object properties are key:value pairs
Access properties with dot notation or bracket notation
Add, change, and delete properties using assignment and delete
Use the in operator to check if a property exists