JSCORE day_ 01(6.30) RegExp 、 Function

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• Include all the attention events in this stage , Related software , Video etc.

Stage content

• 1 Stage : Basics - Cheng Liang The foundation of the server node.js express mysql...

• 2 Stage : WEB Basics HTML CSS SASS AJAX bootstrap Cloud server

• 3 Stage : WEB Page upgrade - JS The core

  • discuss : JS Core design concept of , principle -- Interview questions must be examined

  • New syntax : ES5 6 7 8 ... The new version of the JS grammar , Make code writing easier

  • DOM. jQuery: utilize JS Dynamically operate web pages

  • Vue: Current world ranking Top three web frame , At home No.1

• 4 Stage : Advanced content + Mobile terminal development

• 5 Stage : More advanced framework knowledge

One 、 Declaration upgrade

• JS Of Weirdo Design , The code you see and The actual code executed Dissimilarity

• JS The engine will first hold The declaration operation in the code is promoted to the top of the scope , Then execute the code after adjusting the order

 

 

 

  Interview questions

 

 

• Host environment : JS The environment in which it runs , for example browser and node.js

  • The browser provides window object , It includes all systems attribute / Method

  • window The object is called Global object / Global scope

 

 

Local scope

Function in Runtime temporary Generated objects , Used to store variables declared in functions

• Scope : The name of an object with special functions

  • Global scope : The method of storing the system / attribute -- window

  • Local scope : Function execution time Temporarily generated objects , Stored the variables declared in the function

    • Need a browser Breakpoint debugging function , To see

• Scope chain : When the scope is nested at multiple levels , Using a variable will follow Nearby principle Give priority to the nearest one in the The upper scoped

 

  Closure Closure:

• When a function is declared , I will use myself Variables from other scopes , The scope is saved in its own scopes In the attribute

• Why? : Avoid destruction

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• What can we do with closure features ?

  • Make private variables for functions , Avoid global pollution

• shortcoming : Waste of memory To store closure scope for a long time

• arguments: A hidden attribute of the function

  • effect : Store the arguments of all functions

  • application :

    • Make a function with an indefinite number of arguments -- For example, find the maximum value

    • function overloading : Using arguments Number / type Different , Implement different code logic

      • To make a multi-function Function of

 

 

  Application of closures

 

 

 

 

 

arguments

Function , Hide one of its own properties / Variable

• effect : Save the function received All arguments

• Application scenarios :

  • Make a function with an indefinite number of arguments , for example : For maximum

  • function overloading : Making multifunctional functions , According to the number of arguments or type Different , Make internal judgments Then execute different code logic

 

function overloading

 

this

• this: A property in the function , Represents the object where the function is used

  • Rough understanding

    • object . function (): Functional this Is the object in front

    • function (): this Namely window

 

 

 

Reference type

• Reference type : The object is address passing , Reference type

 

 

 

Shallow copy

 

 

Attribute access