JavaScript Object
All things are JavaScript objects: strings, numbers, arrays, functions /en.
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:
var x=message.length;
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:
var x=message.toUpperCase();
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:
Examples
person.firstname="John";
person.lastname="Doe";
person.age=50;
person.eyecolor="blue";
Alternative syntax (using object literals):
Examples
Using the object constructor
This example uses the function to construct objects:
Examples
{
this.firstname=firstname;
this.lastname=lastname;
this.age=age;
this.eyecolor=eyecolor;
}
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:
var myMother=new person("Sally","Rally",48,"green");
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:
person.lastname="Doe";
person.age=30;
person.eyecolor="blue";
x=person.firstname;
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.
Now you can try:
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 /en. in loop
JavaScript for /en. in statement to loop through the object's properties.
grammar
for (variable in object)
{
执行的代码……
}
Note: for /en. in loop code block will be executed once for each property.
Examples
Loop through the properties of an object:
Examples
for (x in person)
{
txt = txt + person [x];
}
