JavaScript Object
JavaScript objects are data with properties and methods.
Objects, Properties and Methods in Real Life
In real life, a car is an object.
The object has its properties, such as weight and color, and methods such as start and stop:
| Object | Attribute | Method |
|---|---|---|
 | car.name = Dodge car.model = Challenger car.weight = 1550kg car.color = red | car.start() car.drive() car.brake() car.stop() |
All cars have these attributes, but the attributes of each car are different.
All cars have these methods, but they are executed at different times.
JavaScript Object
In JavaScript, almost everything is an object.
 | In JavaScript, objects are very important. When you understand objects, you can understand JavaScript. |
|---|
You have learned the assignment of JavaScript variables.
The following code sets the value of the variable car to "Dodge":
var car = "Dodge";
An object is also a variable, but the object can contain multiple values (multiple variables), and each value is presented as a name:value pair.
var car = {name:"Dodge", model:"Challenger", color:"red"};
In the above example, 3 values ("Dodge", "Challenger", "red") are assigned to the variable car.
| JavaScript Objects are containers for variables. |
|---|
Object Definition
You can use characters to define and create JavaScript objects:
Example
var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};It is defined that JavaScript objects can span multiple lines, and spaces and line breaks are not necessary:
Example
var person = {
firstName:"John",
lastName:"Doe",
age:50,
eyeColor:"blue"
};Object Attributes
It can be said that "JavaScript objects are containers for variables".
However, we usually think that "JavaScript objects are containers for key-value pairs."
Key-value pairs are usually written as name: value (key and value are separated by colons).
Key-value pairs in JavaScript objects are usually referred to as object properties .
| JavaScript objects are containers for attribute variables. |
|---|
The writing method of object key-value pair is similar to:
Associative arrays in PHP
Dictionary in Python
Hash table in C language
Hash mapping in Java
Hash tables in Ruby and Perl
Access Object Properties
You can access object properties in two ways:
Example 1
person.lastName;
Example 2
person["lastName"];
Object Method
The method of an object defines a function and is stored as an attribute of the object.
Object methods are called by adding () (as a function).
This instance accesses the fullName() method of the person object:
Example
name = person.fullName();
If you want to access the fullName property of the person object, it will be returned as a string defining a function:
Example
name = person.fullName;
| JavaScript objects are containers for properties and methods. |
|---|
In subsequent tutorials you will learn more about functions, properties and methods.
Access Object Method
You can create object methods using the following syntax:
methodName : function () {
// code
}
You can access object methods using the following syntax:
Example
objectName.methodName()
Usually fullName() is used as a method of the person object, and fullName is used as an attribute.
If you use the fullName attribute without adding () , it will return the definition of the function:
Example
objectName.methodName
There are many ways to create, use, and modify JavaScript objects.
There are also many ways to create, use and modify properties and methods.
| In subsequent tutorials, you will learn more about objects. |
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