JavaScript Object

All things are JavaScript objects: strings, numbers, arrays, functions ...

In addition, JavaScript allows custom objects.

Everything is an object

JavaScript provides several built-in objects, such as String, Date, Array, and so on. Only with special data type object properties and methods.

• Boolean can be an object.
• Numeric type can be an object.
• String can also be an object
• Date is an object
• Mathematics and regular expressions are objects
• An array is an object
• Even the object function may be

JavaScript Object

Object is just a special kind of data. Objects have properties and methods.

Property access objects

Property is a value associated with an object.

Access object attribute syntax is:

This example uses the length property of the String object to get the length of the string:

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

Object Access Method

The method is an operation that can be performed on the object.

You can call the method using the following syntax:

This example uses the toUpperCase String object () method to convert the text to uppercase:

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

Create a JavaScript object

Through JavaScript, you can define and create your own objects.

Create a new object in two different ways:

• Define and create an instance of an object
• Use functions to define the object, and then create a new object instance

Create a direct instance

This example creates a new instance of the object and add four properties:

Alternative syntax (using object literals):

Using the object constructor

This example uses the function to construct objects:

In JavaScript, this usually points to a function that we are executing itself, or an object that points to the function belongs to (run-time)

Create a JavaScript object instance

Once you have the object constructor, you can create a new instance of the object, like this:

The properties to the JavaScript objects

You can assign an object, add new attributes to existing objects:

Suppose personObj already exists - which you can add these new attributes: firstname, lastname, age and eyecolor:

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

The method to add objects to JavaScript

The method is simply attached to the object's function.

In the method of the constructor function inside the definition of an object:

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;
	}
}

() Value of the function name of the person assigned to changeName lastname properties.

JavaScript classes

JavaScript is an object-oriented language, but JavaScript does not use class.

In JavaScript, the class is not created, nor to create an object (as in the other object-oriented languages) through the class.

JavaScript-based prototype, rather than class-based.

JavaScript for ... in loop

JavaScript for ... in statement to loop through the object's properties.

grammar

for (variable in object)
{
	执行的代码……
}

Note: for ... in loop code block will be executed once for each property.

Examples

Loop through the properties of an object: