linux环境node.js和npm install的安装和使用

Installation on a Mac or Linux

In order to install everything on a Mac, we’ll be running commands in Terminal.app, and Linux distributions vary.

Install Node.js and npm

We’re going to use Node Version Manager (nvm) to install Node.js and npm.

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.1/install.sh | bash

Open the ~/.bash_profile file, and make sure source ~/.bashrc is written in there somewhere. Restart the terminal.

Run the install command.

nvm install node

Run the use command.

nvm use node

Now using node v8.2.0 (npm v5.3.0)

Now that Node.js and npm are installed, test them by typing node -v and npm -v.

All set.

Create a Project

At this point, you’re set to start setting up Gulp, Webpack, Browserify, or whatever your aim is. We can also create a simple project to test that everything is working properly.

Initialize Project

Navigate to the directory in which you want your project to exist – in my case, sites/node-test.

cd sites/node-test

Now initalize a new project with npm.

npm init

The following will pop up in the terminal, and prompt you for a few

This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.

See `npm help json` for definitive documentation on these fields
and exactly what they do.

Use `npm install <pkg>` afterwards to install a package and
save it as a dependency in the package.json file.

First, it will ask for a package name.

node-test

Version number.

1.0.0

Description.

Creating my first "Hello, World!" Node project.

The rest you can just press enter and skip. Now you’ll notice we have a package.json file that contains all the information we entered.

{
  "name": "node-test",
  "version": "1.0.0",
  "description": "Creating my first \"Hello, World!\" Node project.",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Tania Rascia",
  "license": "ISC"
}

A package.json is a file that contains metadata about the project, and handles the dependencies (additional software and modules) of the project.

Now, we’re going to install our first dependency – a very important and useful package called left-pad, which will add white space to the left side of a string, adding up to a number.

For example, writing this:

leftPad('String', 10)

Will output this:

console

String

left-pad is a package on npm, which as we stated previously contains the registry for all publicly available packages.

Install dependencies

To install a dependency with npm, we use the command npm install dependency-name-here. Now, simply running npm install will download the dependency, but it won’t save it to the project. Since we’ve already created our package.json, we’ll use the flag --save to install the dependency and add it to package.json.

npm install left-pad --save

As long as you ran this command inside the project directory, it will successfully install the dependency by creating a node_modules directory. It will also create a package-lock.json file, which we can ignore. Finally, it updated our package.json file with a new line.

"dependencies": {
  "left-pad": "^1.1.3"
}

Now the project recognizes the left-pad dependency as existing

You can also run npm install --save-dev to specify that the dependency will only be used for development (not production) purposes.

Run Node in the terminal

Let’s create index.js in the root of our directory. This is everything you should have now:

For future reference, don’t bother looking in the node_modules rabbit hole. It will get really overwhelming with bigger projects.

In order to use a dependency, we use require() and put it in a variable, like so:

const leftPad = require('left-pad')

This will be the entirety of our index.js file, in which we require left-pad, run a leftPad() function, and send it to the console.

const leftPad = require('left-pad') // Require left pad
const output = leftPad('Hello, World!', 15) // Define output

// Send output to the console
console.log(output)

Since Node.js is not recognized by the browser, we’ll be testing this in the console. In your shell, run the node command followed by the filename in the root of your project.

node index.js

If everything went well, you should have printed Hello, World! to the console, with two spaces on the left.

Hello, World!

Conclusion

In this tutorial, we learned the following:

• What Node.js is
• What npm is
• How to install Node.js and npm on Windows or Mac
• How to make a local project
• How to install a dependency with npm
• How to run a file using a node_modules dependency in a shell

If you got lost at any point, view the source on GitHub.

With this knowledge, you’re ready to start using Gulp, Grunt, Webpack, Browserify, or anything else that depends on Node.js or npm.

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