express-handbook.pdf一份很好的Express英文文档，帮助你更快的学习和梳理Ex

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详细说明：一份很好的Express英文文档，帮助你更快的学习和梳理Express知识The Express Handbook The Express Handbook The Express Handbook follows the 80/20 rule: learn in 20%of the time the 80% of a topic I find this approach gives a well-rounded overview. This book does not try to cover everything under the sun related to Express. If you think some specific topic should be included, tell me You can reach me on Twitter flaviocopes I hope the contents of this book will help you achieve what you want: learn the basics Express This book is written by Flavio. I publish web development tutorials every day on my website flaviocopes. com Enjoy Express overview Express overview Express is a Node. js Web Framework. Node js is an amazing tool for building networking services and applications. Express builds on top of its features to provide easy to use functionality that satisfy the needs of the Web server use case EXPKESS Express is a Node. js Web Framework Node js is an amazing tool for building networking services and applications Express builds on top of its features to provide easy to use functionality that satisfy the needs of the web server use case It's Open Source, free, easy to extend, very performant, and has lots and lots of pre-built packages you can just drop in and use, to perform all kind of things Installation You can install Express into any project with npm Express overview npm install express --save or yarn yarn add express Both commands will also work in an empty directory, to start up your project from scratch although npm does not create a package, json file at all, and Yarn creates a basic one Just run npm init or yarn init if you re starting a new project from scratch Hello world We're ready to create our first Express Web Server Here is some code const express require('express) const app = express() app. get(/,(reg, res)=> res send( Hello world! ) app. listen(3000,(=> console. log( Server ready ) Save this to an index. js file in your project root folder, and start the server using node index. js You can open the browser to port 3000 on localhost and you should see the Hello world! message. Learn the basics of Express by understanding the hello world code Those 4 lines of code do a lot behind the scenes First, we import the express package to the express value We instantiate an application by calling its app() method Once we have the application object, we tell it to listen for Get requests on the path, using the get() method Express overview There is a method for every Http verb get(), post(), put(), delete(), patch() app. get(/( res)=> t app. post(/,(reg, res)=>[/**/]) app. put( )=>{/*x/1) )=>{/**/}) app. patch(/,(req, res)=>[/x*/3) Those methods accept a callback function, which is called when a request is started, and we need to handle it We pass in an arrow function (reg, res)=> res send( Hello World! Express sends us two objects in this callback, which we called req and res, that represent the Request and the Response objects RequestisthehttprequestItcangiveusalltheinfoaboutthatincludingtherequest parameters, the headers, the body of the request, and more Responseisthehttpresponseobjectthatwellsendtotheclient What we do in this callback is to send the Hello world! string to the client, using the Response. send()method This method sets that string as the body, and it closes the connection The last line of the example actually starts the server, and tells it to listen on port 3000.We pass in a callback that is called when the server is ready to accept new requests Request parameters Request parameters a handy reference to all the request object properties and how to use them Request parameters I mentioned how the request object holds all the Http request information These are the main properties you'll likely use Property Description app holds a reference to the Express app object baseUrl the base path on which the app responds contains the data submitted in the request body(must be parsed and populated manually before you can access it contains the cookies sent by the request (needs the cookie-parser cookIes middleware) hostname the server hostname . Ip the server P method thehttpmethodused params the route named parameters path the Url path protocol the request protocol query an object containing all the query strings used in the request secure true if the request is secure(uses Https signed Cookies contains the signed cookies sent by the request(needs the cookie parser middleware true if the request is an XmlhTtpreqUest How to retrieve the get query string parameters using Express The query string is the part that comes after the URl path and starts with a question mark Example: Request parameters ?name=flavio Multiple query parameters can be added using ?name=flavio&age=35 How do you get those query string values in Express? Express makes it very easy by populating the Request query object for us const express require(express) const app express() app. get(/,(req res)=> i console. log (req. query) app. listen (8080) This object is filled with a property for each query parameter If there are no query params, it's an empty object This makes it easy to iterate on it using the for. in loop for (const key in reg. query)i console. log(key, reg. query lkey ]) This will print the query property key and the value You can access single properties as well req. query name //flavio req. query age //35 How to retrieve the POST query string parameters using Express Post query parameters are sent by Http clients for example by forms or when performing a POST request sending data How can you access this data? Request parameters If the data was sent as JSON, using Content-Type: application/json, you will use the express json( middleware const express require(express) const app express( app. use(express.]son()) If the data was sent as JSoN, using Content-Type: application/x-Www-form-urlencoded, you will use the express urlencode( middleware const express require(express) const app expresso app. use(express urlencode() In both cases you can access the data by referencing it from Request body app. post( /form,(reg, res)=>t const name = req. body.name Note: older Express versions required the use of the body-parser module to process POST data. This is no longer the case as of Express 4. 16(released in September 2017) nd later versions Sending a response Sending a response How to send a response back to the client using Express In the Hello World example we used the Response. send() method to send a simple string as a response, and to close the connection (reg, res)=> res send('Hello world! If you pass in a string, it sets the Content-Type header to text/html if you pass in an object or an array, it sets the application/json Content-Type header, and parses that parameter into JSON send()automatically sets the Content-length Http response header send()also automatically closes the connection Use end to send an empty response An alternative way to send the response, without any body, it's by using the Response. end( method esend() Set the Http response status Use the Response status() res status(404).endo res status(404), send( File not found sendstatus(is a shortcut res. sendstatus(200) //=== res status(200). send('OK) res. sendstatus(403 //=== res, status(403). send('Forbidden

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