Setting up a Node development environment 配置更新NodeJS和NPM环境

by tabtuon Posted on

https://developer.mozilla.org/en-US/docs/Learn/Server-side/Express_Nodejs/development_environment

Installing NodeSection

In order to use Express you will first have to install Nodejs and the Node Package Manager (NPM) on your operating system. The following sections explain the easiest way to install the Long Term Supported (LTS) version of Nodejs on Ubuntu Linux 16.04, macOS, and Windows 10.

Tip: The sections below show the easiest way to install Node and NPM on our target OS platforms. If you’re using another OS or just want to see some of the other approaches for the current platforms then see Installing Node.js via package manager (nodejs.org).

Windows and macOSSection

Installing Node and NPM on Windows and macOS is straightforward because you can just use the provided installer:

  1. Download the required installer:
    1. Go to https://nodejs.org/en/
    2. Select the button to download the LTS build that is “Recommended for most users”.
  2. Install Node by double-clicking on the downloaded file and following the installation prompts.

Ubuntu 18.04Section

The easiest way to install the most recent LTS version of Node 10.x is to use the package manager to get it from the Ubuntu binary distributions repository. This can be done very simply by running the following two commands on your terminal:

curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash - 
sudo apt-get install -y nodejs

Warning: Don’t install directly from the normal Ubuntu repositories because they contain very old versions of node.

Testing your Nodejs and NPM installationSection

The easiest way to test that node is installed is to run the “version” command in your terminal/command prompt and check that a version string is returned:

>node -v
v10.15.1

The Nodejs package manager NPM should also have been installed, and can be tested in the same way:

>npm -v
6.4.1

As a slightly more exciting test let’s create a very basic “pure node” server that simply prints out “Hello World” in the browser when you visit the correct URL in your browser:

  1. Copy the following text into a file named hellonode.js. This uses pure Node features (nothing from Express) and some ES6 syntax://Load HTTP module const http = require("http"); const hostname = '127.0.0.1'; const port = 3000; //Create HTTP server and listen on port 3000 for requests const server = http.createServer((req, res) => { //Set the response HTTP header with HTTP status and Content type res.statusCode = 200; res.setHeader('Content-Type', 'text/plain'); res.end('Hello World\n'); }); //listen for request on port 3000, and as a callback function have the port listened on logged server.listen(port, hostname, () => { console.log(`Server running at http://${hostname}:${port}/`); });The code imports the “http” module and uses it to create a server (createServer()) that listens for HTTP requests on port 3000. The script then prints a message to the console about what browser URL you can use to test the server. The createServer() function takes as an argument a callback function that will be invoked when an HTTP request is received — this simply returns a response with an HTTP status code of 200 (“OK”) and the plain text “Hello World”.Note:  Don’t worry if you don’t understand exactly what this code is doing yet! We’ll explain our code in greater detail once we start using Express!
  2. Start the server by navigating into the same directory as your hellonode.js file in your command prompt, and calling node along with the script name, like so:>node hellonode.js Server running at http://127.0.0.1:3000/
  3. Navigate to the URL http://127.0.0.1:3000 . If everything is working, the browser should simply display the string “Hello World”.

Using NPMSection

Next to Node itself, NPM is the most important tool for working with Node applications. NPM is used to fetch any packages (JavaScript libraries) that an application needs for development, testing, and/or production, and may also be used to run tests and tools used in the development process. 

Note: From Node’s perspective, Express is just another package that you need to install using NPM and then require in your own code.

You can manually use NPM to separately fetch each needed package. Typically we instead manage dependencies using a plain-text definition file named package.json. This file lists all the dependencies for a specific JavaScript “package”, including the package’s name, version, description, initial file to execute, production dependencies, development dependencies, versions of Node it can work with, etc. The package.json file should contain everything NPM needs to fetch and run your application (if you were writing a reusable library you could use this definition to upload your package to the npm respository and make it available for other users).

Adding dependenciesSection

The following steps show how you can use NPM to download a package, save it into the project dependencies, and then require it in a Node application.

Note: Here we show the instructions to fetch and install the Express package. Later on we’ll show how this package, and others, are already specified for us using the Express Application Generator. This section is provided because it is useful to understand how NPM works and what is being created by the application generator.

  1. First create a directory for your new application and navigate into it:mkdir myapp cd myapp
  2. Use the npm init command to create a package.json file for your application. This command prompts you for a number of things, including the name and version of your application and the name of the initial entry point file (by default this is index.js). For now, just accept the defaults:npm initIf you display the package.json file (cat package.json), you will see the defaults that you accepted, ending with the license.{ "name": "myapp", "version": "1.0.0", "description": "", "main": "index.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" }, "author": "", "license": "ISC" }
  3. Now install Express in the myapp directory and save it in the dependencies list of your package.json file
  4. npm install expressThe dependencies section of your package.json will now appear at the end of the package.json file and will include Express.{ "name": "myapp", "version": "1.0.0", "description": "", "main": "index.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" }, "author": "", "license": "ISC", "dependencies": { "express": "^4.16.4" } }
  5. To use the Express library you call the require() function in your index.js file to include it in your application. Create this file now, in the root of the “myapp” application directory, and give it the following contents:const express = require('express') const app = express(); app.get('/', (req, res) => { res.send('Hello World!') }); app.listen(8000, () => { console.log('Example app listening on port 8000!') });This code shows a minimal “HelloWorld” Express web application. This imports the “express” module using require() and uses it to create a server (app) that listens for HTTP requests on port 8000 and prints a message to the console explaining what browser URL you can use to test the server. The app.get() function only responds to HTTP GET requests with the specified URL path (‘/’), in this case by calling a function to send our Hello World! message.
  6. You can start the server by calling node with the script in your command prompt:>node index.js Example app listening on port 8000
  7. Navigate to the URL (http://127.0.0.1:8000/). If everything is working, the browser should simply display the string “Hello World!”.

Development dependenciesSection

If a dependency is only used during development, you should instead save it as a “development dependency” (so that your package users don’t have to install it in production). For example, to use the popular JavaScript Linting tool eslint you would call NPM as shown:

npm install eslint --save-dev

The following entry would then be added to your application’s package.json:

"devDependencies": {
    "eslint": "^4.12.1"
  }

Note: “Linters” are tools that perform static analysis on software in order to recognise and report adherence/non-adherance to some set of coding best practice.

Running tasksSection

In addition to defining and fetching dependencies you can also define named scripts in your package.json files and call NPM to execute them with the run-script command. This approach is commonly used to automate running tests and parts of the development or build toolchain (e.g., running tools to minify JavaScript, shrink images, LINT/analyse your code, etc).

Note: Task runners like Gulp and Grunt can also be used to run tests and other external tools.

For example, to define a script to run the eslint development dependency that we specified in the previous section we might add the following script block to our package.jsonfile (assuming that our application source is in a folder /src/js):

"scripts": {
  ...
  "lint": "eslint src/js"
  ...
}

To explain a little further, eslint src/js is a command that we could enter in our terminal/command line to run eslint on JavaScript files contained in the src/js directory inside our app directory. Including the above inside our app’s package.json file provides a shortcut for this command — lint.

We would then be able to run eslint using NPM by calling:

npm run-script lint
# OR (using the alias)
npm run lint

This example may not look any shorter than the original command, but you can include much bigger commands inside your npm scripts, including chains of multiple commands. You could identify a single npm script that runs all your tests at once.

Installing the Express Application GeneratorSection

The Express Application Generator tool generates an Express application “skeleton”. Install the generator using NPM as shown (the -g flag installs the tool globally so that you can call it from anywhere):

npm install express-generator -g

To create an Express app named “helloworld” with the default settings, navigate to where you want to create it and run the app as shown:

express helloworld

Note: You can also specify the template library to use and a number of other settings. Use the help command to see all the options:

express --help

NPM will create the new Express app in a sub folder of your current location, displaying build progress on the console. On completion, the tool will display the commands you need to enter to install the Node dependencies and start the app.

The new app will have a package.json file in its root directory. You can open this to see what dependencies are installed, including Express and the template library Jade:

{
  "name": "helloworld",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www"
  },
  "dependencies": {
    "cookie-parser": "~1.4.3",
    "debug": "~2.6.9",
    "express": "~4.16.0",
    "http-errors": "~1.6.2",
    "jade": "~1.11.0",
    "morgan": "~1.9.0"
  }
}

Install all the dependencies for the helloworld app using NPM as shown:

cd helloworld
npm install

Then run the app (the commands are slightly different for Windows and Linux/macOS), as shown below:

# Run the helloworld on Windows with Command Prompt
SET DEBUG=helloworld:* & npm start

# Run the helloworld on Windows with PowerShell
SET DEBUG=helloworld:* | npm start

# Run helloworld on Linux/macOS
DEBUG=helloworld:* npm start

The DEBUG command creates useful logging, resulting in an output like that shown below.

>SET DEBUG=helloworld:* & npm start

> helloworld@0.0.0 start D:\Github\expresstests\helloworld
> node ./bin/www

  helloworld:server Listening on port 3000 +0ms

Open a browser and navigate to http://127.0.0.1:3000/ to see the default Express welcome page.

Express - Generated App Default Screen

We’ll talk more about the generated app when we get to the article on generating a skeleton application.

SummarySection

You now have a Node development environment up and running on your computer that can be used for creating Express web applications. You’ve also seen how NPM can be used to import Express into an application, and also how you can create applications using the Express Application Generator tool and then run them.

In the next article we start working through a tutorial to build a complete web application using this environment and associated tools.

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