Welfare, let me introduce you to someone

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Series column ：【JavaScript】
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Long time no see , I miss you so much ！
Hello everyone ！ I'm brother Yang
It's Valentine's day , But some brothers told me he had no object , How can this work ？ therefore , I took out what I pressed at the bottom of the box , I must introduce him well , Teach him an object-oriented outline , If he is not satisfied with the object , Don't worry , Then let him customize the object , One step at a time , Big brother read my article , I was moved to tears . Although I have no object , But he introduced someone to others , This is giving roses to others and leaving fragrance in your hands , Life is complete .

If your good brother doesn't have a date on Valentine's Day , please give the thumbs-up , Collection This article , Then put this article forward Give it to him , I believe he will thank you Act of kindness ！

One 、 Object-oriented overview

Process and object oriented

To accomplish one thing to illustrate what is process oriented and object-oriented .

• Process oriented solutions ： Focus on specific steps , Only follow step by step , To be able to complete this thing .
• Object oriented solutions ： Focus on one object , These objects perform their respective duties , We just give orders , Can command these objects to help us complete the task .

summary ：

• For process oriented thinking , We play the executor , Everything must be done by yourself .
• For object-oriented ideas , We play the commander , Just find the corresponding object , Let them help us do specific things .

• Disadvantages of process oriented thinking
  The code written is some variables and functions , With the continuous increase of program functions , There will be more and more variables and functions , At this time, it is easy to encounter the problem of naming conflict , Because the codes of various functions are intertwined , It leads to code structure confusion , Become difficult to understand 、 Maintenance and reuse .

• Advantages of object-oriented thinking
  You can encapsulate the operation code of the same kind of things into objects , Take the variables and functions used as the properties and methods of the object , Then call... Through an object , This makes the code structure clear 、 distinct .

Object oriented features

encapsulation

encapsulation ： It refers to hiding the internal implementation details , Only open the operation interface .

Interface ： It's the method of the object , No matter how complex the interior of the object is , Users only need to know how to use these interfaces .

give an example ： Computers are very sophisticated electronic devices , The implementation principle is also very complex , Users do not need to know these details when using , As long as you operate the keyboard and mouse, you can use .

advantage ： No matter how many times the code inside an object has been modified , As long as you don't change the interface , It will not affect the code written when using this object .

inheritance

Inherit ： It refers to that one object inherits the members of another object , So as to expand without changing another object .

give an example 1： The relationship between animals and cats and dogs , Human reproduction, etc .

give an example 2：String An object is an abstraction of all strings , All strings have toUpperCase() Method , Used to convert a string to uppercase , This method is actually inherited from String object .

advantage ：

• The function can be extended on the premise of maintaining interface compatibility .
• Enhanced code reusability , Facilitate the modification and supplement of procedures .

polymorphism

polymorphic ： It means that the same operation acts on different objects , There will be different execution results .

understand ： actually JavaScript Designed as a weakly typed language （ That is, a variable can store any type of data ）, It's the expression of polymorphism .

for example , Numbers 、 Array 、 Functions have toString() Method , When the method is called with different objects , The results are different .

Tips ： In object orientation , The implementation of polymorphism is often inseparable from inheritance , This is because when multiple objects inherit the same object , You get the same method , Then change the execution result of the method with the same name according to the difference of each object .

Tips ： Although object-oriented has encapsulation 、 Inherit 、 These design ideas , However, it does not mean that as long as these characteristics are met, excellent programs can be designed , Developers also need to consider how to make rational use of these features .

example 1： When packaging , How to provide a complete and minimal interface for external callers , So that the external caller can get the desired function smoothly , There is no need to study the internal details .

example 2： When designing for inheritance and polymorphism , For multiple different sub objects that inherit the same object , How to design a set of the same method to operate .

Two 、 Custom object

Object definition

grammar ： Objects are defined by “{ }” Grammar realizes .

form ： Object as object member （ Properties and methods ） constitute , Multiple members are separated by commas .

member ： The members of the object are stored in the form of key value pairs {} in .

Be careful

“{ }” Syntax is also called literal syntax of objects , The so-called literal quantity refers to a quantity representing data and types written directly in the source code , Such as 123（ Numerical type ）、‘123’（ Character ）、[123]（ Array ） It's all literal .

JSON data format

JSON： JavaScript Object Notation,JavaScript Object symbols .

purpose ： Applied to data storage and interaction .

grammar ： JSON Is a string , Wrap the member name and string value of the object in double quotation marks .

JSON The difference from the object ：

• JSON Is a string .
• JSON Not only can it be used to save objects , You can also save numbers 、 character string 、 Arrays and other types of data .

Access object members

grammar ： object . member .

Variable member name syntax ： object [ Variable name ] = value .

Object member traversal

grammar ：for…in.

• Variable k Saved the name of each object member .
• obj[k] Access the value of the member property .
• objk Calling a member method .

Determine whether the object member exists

• When you need to judge whether a member in an object exists , have access to in Operator .
• Returns... When the member of the object exists true, Return... When not present false.
  

If you think this article has some inspiration for you , Might as well give the thumbs-up 、 Collection 、 Leaving a message. support , Your support will be the biggest driving force for me to continue my creation ️️️

Because the author level is limited , Mistakes and inaccuracies are inevitable , I also want to know these mistakes , I sincerely hope that readers will criticize and correct ！

Last , I wish all lovers a happy ending , With all of you xdm You will find the right person this year ！（ This is not a concern ）