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
See Also
What are JavaScript Objects?
What are Object Methods?
What is this in Objects?
How to Display JavaScript Objects
What is an Object Constructor?
Advanced Chapters
JavaScript Object Definitions
JavaScript Object Advanced this
JavaScript Object Iterations
JavaScript Object Getters & Setters
JavaScript Object Management
JavaScript Object Protection
JavaScript Object Prototypes
JavaScript Object Reference