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Node series: first meeting nodejs

2021-02-23 17:59:16 gentle and agree-able

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One 、 Introduce

  • Nodejs Is based on  Google V8  Engine Javascript Running environment ;

    It makes JavaScript You can develop back-end programs , It can achieve almost all the functions that other back-end languages can achieve ;
  • Nodejs What I'm good at is dealing with high concurrency ;

    stay Java、PHP perhaps .net Etc. in the server-side language , A new thread will be created for each client connection , And each thread costs about 2MB Memory . in other words , Theoretically , One 8GB The maximum number of users that a memory server can connect to at the same time is 4000 about . Must let Web Applications support more users , You need to increase the number of servers , Web Of course, the hardware cost of the application goes up .Nodejs Do not create a new thread for each client connection , And just one thread , When there are users connected , To trigger an internal event , Through non blocking I/O、 Event driven mechanism , Make it lightweight and efficient , One 8GB Memory servers , Can handle more than at the same time 4 Million user connections .
  • Nodejs With a powerful and flexible package manager (node package manager,npm);

    There are already tens of thousands of third-party modules , There is a website development framework , Yes  MySQL、MongoDB  Database interface , There are template language parsing 、CSS  Generation tool 、 mail 、 encryption 、 graphics 、 Debugging support , There are even graphical user interfaces and operating systems API Tools .

Two 、 Why learn Nodejs

  • Large users : We can't count Nodejs Software downloads , But we can pass Nodejs frame Express To analyze the download amount of Nodejs The number of users is amazing .

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  • Simple :Nodejs Grammar is all about it js grammar , As long as you know JS You can learn the basics Nodejs The backend development , bring Nodejs It has a short development cycle 、 Low development cost 、 The advantages of low learning cost .

    Node.js Medium JavaScript It's just Core JavaScript, Or rather, ECMAScript An implementation of , It doesn't contain DOM、BOM perhaps Client JavaScript. This is because Node.js Not running in browser , So you don't need to use many of the features in the browser , There is no such thing as  JavaScript  Browser compatibility issues , You can use  JavaScript  All the characteristics of language .

3、 ... and 、 install

Nodejs The installation is the same as normal software , Official website Download the latest version , Proposed installation Current edition ,LTS There's something new in the version API Can't use , Just go to the next step , After installation , Open the console to run ’node -v‘ Check whether the installation is successful , here npm It's already installed .

Sometimes you may want to try some interesting features in a new version , But also want to maintain a relatively stable environment . Based on this demand ,Node.js The community developed a multi version Manager , Used to maintain multiple versions of... On a single machine Node.js example , Easy to switch on demand . There are many different implementations right now ,https://github.com/creationix/nvm perhaps https://github.com/visionmedia/n.

Proposed installation nvm, Manage different versions of node and npm
1.mac Refer to the link for the installation method of https://segmentfault.com/a/11...
2.windows Direct installation nvm-windows  that will do ( Be sure to uninstall the installed before installation Nodejs, Otherwise there will be conflict )

Four 、 Start a simple Nodejs The server

Create a new one app.js file , On the command line through node app.js, You can run a server , Access... In browser access http://127.0.0.1:3000/, You can see that Hello Nodejs.

const host = '127.0.0.1';
const port = 3000;
const server = http.createServer((req,res) => {
 res.statusCode = 200; res.setHeader('Content-Type', 'text/plain'); res.end('Hello Nodejs');})
​
server.listen(port, host, () => {
 console.log(` The server is running at  http://${host}:${port}/`)})

Full sample code address :https://github.com/wanwan0306/future/tree/main/Demo/NodeJs/1 initial nodejs

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