npm包管理

npm其实是Node.js的包管理工具（node package manager）。

为啥我们需要一个包管理工具呢？因为我们在Node.js上开发时，会用到很多别人写的JavaScript代码。如果我们要使用别人写的某个包，每次都根据名称搜索一下官方网站，下载代码，解压，再使用，非常繁琐。于是一个集中管理的工具应运而生：大家都把自己开发的模块打包后放到npm官网上，如果要使用，直接通过npm安装就可以直接用，不用管代码存在哪，应该从哪下载。

更重要的是，如果我们要使用模块A，而模块A又依赖于模块B，模块B又依赖于模块C和模块D，npm可以根据依赖关系，把所有依赖的包都下载下来并管理起来。否则，靠我们自己手动管理，肯定既麻烦又容易出错。

npm的基础使用

npm的指令其实常用的并不多官方文档；列出来如下面：

access
Set access level on published packages
adduser
```
Add a registry user account
```
audit
```
Run a security audit
```
bin
```
Display npm bin folder
```

bugs

Bugs for a package in a web browser maybe

build
```
Build a package
```
bundle
```
REMOVED *已删除*
```
cache
```
Manipulates packages cache
```
ci
```
Install a project with a clean slate
```
completion
```
Tab Completion for npm
```
config
```
Manage the npm configuration files
```
dedupe
```
Reduce duplication
```
deprecate
```
Deprecate a version of a package
```
dist-tag
```
Modify package distribution tags
```

docs

Docs for a package in a web browser maybe

doctor
```
Check your environments
```
edit
```
Edit an installed package
```
explore
```
Browse an installed package
```
help-search
```
Search npm help documentation
```
help
```
Get help on npm
```
hook
```
Manage registry hooks
```
init
```
create a package.json file
```

install-ci-test

Install a project with a clean slate and run tests

install-test
```
Install package(s) and run tests
```
install
```
Install a package
```
link
```
Symlink a package folder
```
logout
```
Log out of the registry
```
ls
```
List installed packages
```
npm
```
javascript package manager
```
outdated
```
Check for outdated packages
```
owner
```
Manage package owners
```
pack
```
Create a tarball from a package
```
ping
```
Ping npm registry
```
prefix
```
Display prefix
```

profile

Change settings on your registry profile

prune
```
Remove extraneous packages
```
publish
```
Publish a package
```
rebuild
```
Rebuild a package
```

repo

Open package repository page in the browser

restart
```
Restart a package
```
root
```
Display npm root
```
run-script
```
Run arbitrary package scripts
```
search
```
Search for packages
```

shrinkwrap

Lock down dependency versions for publication

star
```
Mark your favorite packages
```
stars
```
View packages marked as favorites
```
start
```
Start a package
```
stop
```
Stop a package
```

team

Manage organization teams and team memberships

test
```
Test a package
```
token
```
Manage your authentication tokens
```
uninstall
```
Remove a package
```
unpublish
```
Remove a package from the registry
```
update
```
Update a package
```
version
```
Bump a package version
```
view
```
View registry info
```
whoami
```
Display npm username
```

init

初始化创建package.json

npm init [–force|-f|–yes|-y|–scope]
npm init <@scope> (same as npx <@scope>/create)
npm init [<@scope>/] (same as npx [<@scope>/]create-<name>)

search

搜索查看远程npm相关资源包信息

npm search [-l|–long] [–json] [–parseable] [–no-description] [search terms …]
aliases: s, se, find

install

可以是说是install是最为常见的命令官方介绍，

npm install (with no args, in package dir)
npm install [<@scope>/]
npm install [<@scope>/]@
npm install [<@scope>/]@
npm install [<@scope>/]@
npm install :/
npm install
npm install
npm install
npm install

alias: npm i
common options: [-P|–save-prod|-D|–save-dev|-O|–save-optional] [-E|–save-exact] [-B|–save-bundle] [–no-save] [–dry-run]

In global mode (ie, with -g or –global appended to the command), it installs the current package context (ie, the current working directory) as a global package. The -g or –global argument will cause npm to install the package globally rather than locally.

The -f or –force argument will force npm to fetch remote resources even if a local copy exists on disk.

上面的还介绍已经很详细了，所以这里只是讲一下npm install packageName [|--save |--save-prod|--save-dev]的区别；

npm install babel
npm5以前,会把X包安装到node_modules目录中，不会修改package.json的dependencies字段，之后运行npm install命令时，不会自动安装X
npm install babel
npm5以后,会把X包安装到node_modules目录中，会修改package.json的dependencies字段，之后运行npm install命令时，会自动安装X, 线上环境时会被安装
npm install babel -P
-P, –save-prod: Package will appear in your dependencies. This is the default unless -D or -O are present. Package will appear in your dependencies, With the –production flag (or when the NODE_ENV environment variable is set to production), npm will install modules listed in dependencies.
npm install babel -D
Package will appear in your devDependencies，With the –production flag (or when the NODE_ENV environment variable is set to production), npm will not install modules listed in devDependencies. 会把X包安装到node_modules目录中，会在package.json的devDependencies属性下添加X，之后运行npm install命令时，会自动安装X到node_modules目录中，之后运行npm install –production或者注明NODE_ENV变量值为production时，不会自动安装X到node_modules目录中

update

升级某个资源包或者全部资源包到某一个版本或者匹配的最新版本。

npm update [-g] […]
aliases: up, upgrade

uninstall

移除某个资源包

npm uninstall [<@scope>/][@]… [-S|–save|-D|–save-dev|-O|–save-optional|–no-save]
aliases: remove, rm, r, un, unlink

npm包创建、编写、测试、维护

Node出现之前，JavaScript是缺少包结构的。CommonJS致力于改变这种现状，于是定义了包的结构规范。而NPM的出现则是为了在CommonJS规范的基础上，实现解决包的安装卸载，依赖管理，版本管理等问题。require的查找机制明了之后，我们来看一下包的细节。
一个符合CommonJS规范的包应该是如下这种结构：

一个package.json文件应该存在于包顶级目录下
二进制文件应该包含在bin目录下(可选)
JavaScript代码入库是index.js，其他包含在lib目录下
文档应该在doc目录下(可选)
单元测试应该在test目录下(可选)

初始化包

创建包的根目录
1
mkdir testpackage

初始化

1	npm init // 需要进行一些基本配置

编写

创建入口文件
1
touch index.js

编写代码

const updateQueryString = function(url, key, value) {
    let urlParts = url.split('#'),
        hash = '',
        uri = urlParts.shift(),
        re = new RegExp(`([?&])${key}=.*?(&|$)`, 'i'),
        separator = uri.indexOf('?') !== -1 ? '&' : '?',
        encodeKey = encodeURIComponent(key),
        encodeValue = encodeURIComponent(value);

    urlParts.length > 0 && (hash = `#${urlParts.join('#')}`);

    if (uri.match(re)) {
        return uri.replace(re, `$1${encodeKey}=${encodeValue}$2`) + hash;
    } else {
        return `${uri}${separator}${encodeKey}=${encodeValue}${hash}`;
    }
};

// 最后的导出部分
module.exports = {
    updateQueryString
};

测试

创建包的根目录

npm i mocha -D    // 安装测试库
npm i chai -D     // 安装断言库
mkdir test
cd test
touch index.test.js

编写测试代码

const utils = require('./../index.js');
const expect = require('chai').expect;

let {
    updateQueryString
} = utils;

describe('updateQueryString函数的测试', function() {
    it('https://test.com/path?test=11 修改test参数为22 应该等于 https://test.com/path?test=22', function() {
        expect(updateQueryString('https://test.com/path?test=11', 'test', 22)).to.be.equal('https://test.com/path?test=22');
    });
});

运行测试
1
2
cd ..
./node_modules/mocha/bin/mocha

npm包的发布

注册账号npm官网
终端执行 npm login,输入用户名和密码、邮箱
npm publish 发布

Organization包

我们经常可以看到@angular、@ionic他们的包，都可以以@开头，那么我们的可不可以，原来angular、ionic都属于一个组织（Organization）只有新创建一个Organization组织之后，才能创建@testorg/testpackname这样的包！！！

那么我们就可以去官网上创建我们的Organization，命名之后，官方步骤，

初始化
1
npm init --scope=<your_org_name>
npm init foo -> npx create-foo
npm init @usr/foo -> npx @usr/create-foo
npm init @usr -> npx @usr/create
修改package.json里面的name字段为@your_org_name/<pkg_name>

发布

1	npm publish --access public // 公开包发布

npm包支持esmodule

使用babel来进行一些现代JavaScript的支持，

创建配置文件
1
touch .babelrc
安装先关包

配置babel

{
  "presets": [
    [
      "@babel/preset-env",
      {
        "targets": {
          "browsers": [
            "last 2 versions",
            "safari >= 7"
          ],
          "chrome": 52,
          "node": "6.10.0"
        },
        "modules": "commonjs",
        "useBuiltIns": "usage"
      }
    ]
  ],
  "plugins": [
    "@babel/plugin-syntax-dynamic-import",
    "@babel/plugin-syntax-import-meta",
    "@babel/plugin-proposal-class-properties",
    "@babel/plugin-proposal-json-strings",
    [
      "@babel/plugin-proposal-decorators",
      {
        "legacy": true
      }
    ],
    "@babel/plugin-proposal-function-sent",
    "@babel/plugin-proposal-export-namespace-from",
    "@babel/plugin-proposal-numeric-separator",
    "@babel/plugin-proposal-throw-expressions",
    "@babel/plugin-proposal-export-default-from",
    "@babel/plugin-proposal-logical-assignment-operators",
    "@babel/plugin-proposal-optional-chaining",
    [
      "@babel/plugin-proposal-pipeline-operator",
      {
        "proposal": "minimal"
      }
    ],
    "@babel/plugin-proposal-nullish-coalescing-operator",
    "@babel/plugin-proposal-do-expressions"
  ]
}

编译
1
./node_modules/.bin/babel src -d lib

最后的测试代码地址test-demo-npm