Understand HTTP transactions and Node modular specifications

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HTTP transaction:

First of all, the HTTP transaction must be described completely The process from request to response:

1. When a user initiates a request, domain name resolution is first performed
2. to obtain the IP corresponding to the domain name After the address, establish a communication connection with the server through the TCP protocol. (Three-way handshake, establishing connection)
3. After the service receives the user request, it performs business processing, and then returns the result after the request to the browser
4. The browser receives the background data (4 times Waving hands, disconnecting) Note: connection:keep-alive always connected

Node modular specification:

Problems solved:

1. Variable pollution : It means that the variables in the two JS files can access each other, resulting in variable coverage
2. Dependency management: It requires manual management and is cumbersome and inefficient
3. The runtime of node javascript`: that is The running environment is divided into two types (browser, Node)

   node standard:

   Each JS file is a module and has an independent scope

   Through require("path" ) to introduce module.exports={things to be exposed}to expose the collective nameInterface

npm package management tool (Node Package Manage)

1. Modify Taobao source: open the command control character and copy npm config set registry https://registry.npm.taobao.org

2. Create a project directory (Folder) myapp, and enter the terminal

3. Terminal project initialization: npx express-generator

4. Terminal installation dependencies:npm install

5. Start the terminal npm start

6. Use the browser to access http://localhost:3000, and check that the access page pops up as success!

Browser modularization specification:

JS introduction specification:

Expose a single: export and the method to be exposed;

##Single introduction: import{Exposed method}from"

path.js";

Batch exposure: export default {Method to be exposed 1, Method to be exposed 2} ;

Batch import: import any value received from "

path.js";

Introduced two methods add, add1 and passed parameters

Note: When the introduced method has the same name as its own method, you can use xx as xx to get an alias

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