包描述文件用于表达非代码相关的信息,它是一个JSON格式的文件——package.json,位于包的根目录下,是包的重要组成部分。而npm的所有行为都与包描述文件的字段息息相关。
CommonJS为package.json文件定义一些必须的字段。
NPM通过该属性进行权限认证。
除了必选字段外,规范还定义了一部分可选的字段
homepage:当前包的网站地址。
os:操作系统支持的列表。这些操作系统的取值包括aix,freebsd,Linux,macos,solaris,vxworks,windows。如果设置了列表为空时,则不对操作系统做任何假设。
CPU:CPU架构的支持列表。
engine:支持的js引擎列表,有效的引擎列表取值包括ejs,flusspferd,gpsee,jsc,spidermonkey,narwhal,node,v8.
builtin:标志当前包是否是内建在底层系统的标准组件。
directories:包目录说明。
implements:实现规范的列表,标志当前包实现了CommonJS的那些规范。
scripts:脚本说明对象。它主要被包管理器用来安装,编译,测试和卸载包。
//示例如下:
"scripts":{
"install":"install.js",
"uninstall":"uninstall.js",
"build":"build.js",
"test":"test.js"
}
包规范的定义可以帮助Node解决依赖包安装的问题,而NPM正是基于该规范进行了实现。最初,NPM工具是有Issac Z.Schlueter单独创建,提供给node服务的Node包管理器,需要单独安装。后来,在v6.3版本时集成进Node中作为默认包管理器,作为软件包的一部分一起安装。
在包描述文件的规范中,NPM实际需要的字段主要有name,version,description,keywords,repositories,author,bin,main,scripts,engines,dependencies,devDependencies。
与包规范的区别在于多了author,bin,main和devDependencies这4个字段。
author:包作者。
bin:一些包作者希望包可以作为命令行工具使用。配置好bin字段后,通过npm install package_name -g
命令可以将脚本添加到执行路径中,之后可以在命令行中直接执行。通过-g命令安装的模块包称为全局模式。
main:模块引入方法require()在引入包时,会优先检查这个字段,并将其作为包中其余模块的入口。如果不存在这个字段,require()方法会查找包目录下的 index.js , index.node , index.json 文件作为默认入口。
devDependencies:一些模块只在开发时需要依赖。配置这个属性,可以提示包的后续开发者安装依赖包。
//以下是node比较有名的框架express项目的package.json文件
{
"name": "express",
"description": "Fast, unopinionated, minimalist web framework",
"version": "4.17.1",
"author": "TJ Holowaychuk ",
"contributors": [
"Aaron Heckmann ",
"Ciaran Jessup ",
"Douglas Christopher Wilson ",
"Guillermo Rauch ",
"Jonathan Ong ",
"Roman Shtylman ",
"Young Jae Sim "
],
"license": "MIT",
"repository": "expressjs/express",
"homepage": "http://expressjs.com/",
"keywords": [
"express",
"framework",
"sinatra",
"web",
"rest",
"restful",
"router",
"app",
"api"
],
"dependencies": {
"accepts": "~1.3.7",
"array-flatten": "1.1.1",
"body-parser": "1.19.0",
"content-disposition": "0.5.3",
"content-type": "~1.0.4",
"cookie": "0.4.0",
"cookie-signature": "1.0.6",
"debug": "2.6.9",
"depd": "~1.1.2",
"encodeurl": "~1.0.2",
"escape-html": "~1.0.3",
"etag": "~1.8.1",
"finalhandler": "~1.1.2",
"fresh": "0.5.2",
"merge-descriptors": "1.0.1",
"methods": "~1.1.2",
"on-finished": "~2.3.0",
"parseurl": "~1.3.3",
"path-to-regexp": "0.1.7",
"proxy-addr": "~2.0.5",
"qs": "6.7.0",
"range-parser": "~1.2.1",
"safe-buffer": "5.1.2",
"send": "0.17.1",
"serve-static": "1.14.1",
"setprototypeof": "1.1.1",
"statuses": "~1.5.0",
"type-is": "~1.6.18",
"utils-merge": "1.0.1",
"vary": "~1.1.2"
},
"devDependencies": {
"after": "0.8.2",
"connect-redis": "3.4.1",
"cookie-parser": "~1.4.4",
"cookie-session": "1.3.3",
"ejs": "2.6.1",
"eslint": "2.13.1",
"express-session": "1.16.1",
"hbs": "4.0.4",
"istanbul": "0.4.5",
"marked": "0.6.2",
"method-override": "3.0.0",
"mocha": "5.2.0",
"morgan": "1.9.1",
"multiparty": "4.2.1",
"pbkdf2-password": "1.2.1",
"should": "13.2.3",
"supertest": "3.3.0",
"vhost": "~3.0.2"
},
"engines": {
"node": ">= 0.10.0"
},
"files": [
"LICENSE",
"History.md",
"Readme.md",
"index.js",
"lib/"
],
"scripts": {
"lint": "eslint .",
"test": "mocha --require test/support/env --reporter spec --bail --check-leaks test/ test/acceptance/",
"test-ci": "istanbul cover node_modules/mocha/bin/_mocha --report lcovonly -- --require test/support/env --reporter spec --check-leaks test/ test/acceptance/",
"test-cov": "istanbul cover node_modules/mocha/bin/_mocha -- --require test/support/env --reporter dot --check-leaks test/ test/acceptance/",
"test-tap": "mocha --require test/support/env --reporter tap --check-leaks test/ test/acceptance/"
},
"__npminstall_done": "Sun Feb 16 2020 11:22:54 GMT+0800 (GMT+08:00)",
"_from": "[email protected]",
"_resolved": "https://registry.npm.taobao.org/express/download/express-4.17.1.tgz"
}