In-depth analysis of object concepts in JavaScript programming, in-depth analysis of javascript

In-depth analysis of object concepts in JavaScript programming, in-depth analysis of javascript

Everything in JavaScript is an object: String, value, array, function...
In addition, JavaScript allows custom objects.
All things are objects
JavaScript provides multiple built-in objects, such as String, Date, and Array. Objects are only special data types with properties and methods.

• A boolean can be an object.
• A numeric type can be an object.
• A string can also be an object.
• Date is an object
• Math and regular expression are also objects
• An array is an object.
• Even functions can be objects.

JavaScript Object

Object is only a special type of data. The object has attributes and methods.
Access Object Attributes
An attribute is an object-related value.
The syntax for accessing object properties is:

objectName.propertyName

In this example, The length attribute of the String object is used to obtain the length of the String:

var message="Hello World!";var x=message.length;

After the preceding code is executed, the value of x is:

12

Method of accessing objects
A method is an action that can be executed on an object.
You can use the following syntax to call a method:

objectName.methodName()

In this example, the toUpperCase () method of the String object is used to convert the text to uppercase:

var message="Hello world!";var x=message.toUpperCase();

After the preceding code is executed, the value of x is:

HELLO WORLD!

Create a JavaScript Object
With JavaScript, you can define and create your own objects.
There are two different ways to create a new object:

1. Define and create an instance of an object
2. Define an object using a function, and then create a new object instance.

Create a direct instance
In this example, a new instance of the object is created and four attributes are added to it:
Instance

person=new Object();person.firstname="John";person.lastname="Doe";person.age=50;person.eyecolor="blue";

Alternative syntax (Use object literals ):
Instance

person={firstname:"John",lastname:"Doe",age:50,eyecolor:"blue"};

Use object constructor
This example uses functions to construct objects:
Instance

function person(firstname,lastname,age,eyecolor){this.firstname=firstname;this.lastname=lastname;this.age=age;this.eyecolor=eyecolor;}

In JavaScript, this usually points to the function we are executing, or to the object to which the function belongs (runtime)
Create a JavaScript object instance
Once you have an object constructor, you can create a new object instance like this:

var myFather=new person("John","Doe",50,"blue");var myMother=new person("Sally","Rally",48,"green");

Add property to JavaScript Object
You can add new attributes to an existing object by assigning values to the object:
Assuming that personObj already exists-you can add these new attributes for it: firstname, lastname, age, and eyecolor:

person.firstname="John";person.lastname="Doe";person.age=30;person.eyecolor="blue";x=person.firstname;

T after the above code is executed, the value of x will be:

John

Add a method to a JavaScript Object
The method is only a function attached to an object.
Methods for defining objects within the constructor function:

function person(firstname,lastname,age,eyecolor){this.firstname=firstname;this.lastname=lastname;this.age=age;this.eyecolor=eyecolor;this.changeName=changeName;function changeName(name){this.lastname=name;}}

The value of changeName () function name is assigned to the lastname attribute of person.
Now you can try:

myMother.changeName("Doe");