深入理解webpack process.env.NODE_ENV配置

在node中，有全局变量process表示的是当前的node进程。process.env包含着关于系统环境的信息。但是process.env中并不存在NODE_ENV这个东西。NODE_ENV是用户一个自定义的变量，在webpack中它的用途是判断生产环境或开发环境的依据的。

为了查看 process的基本信息，我们可以在文件夹中 新建一个 process.js 文件，在里面加一句代码：console.log(process);然后进入该文件夹，执行 node process.js 可以在命令行中打印如下信息：

$ node process.jsprocess { title: 'node', version: 'v4.4.4', moduleLoadList:   [....], versions:   { http_parser: '2.5.2',   node: '4.4.4',   v8: '4.5.103.35',   uv: '1.8.0',   zlib: '1.2.8',   ares: '1.10.1-DEV',   icu: '56.1',   modules: '46',   openssl: '1.0.2h' }, arch: 'x64', platform: 'darwin', release:   { name: 'node',   lts: 'Argon',   sourceUrl: 'https://nodejs.org/download/release/v4.4.4/node-v4.4.4.tar.gz',   headersUrl: 'https://nodejs.org/download/release/v4.4.4/node-v4.4.4-headers.tar.gz' }, argv:   [ '/Users/tugenhua/.nvm/versions/node/v4.4.4/bin/node',   '/Users/tugenhua/个人demo/process.js' ], execArgv: [], env:   { TERM_PROGRAM: 'Apple_Terminal',   SHELL: '/bin/zsh',   TERM: 'xterm-256color',   TMPDIR: '/var/folders/l7/zndlx1qs05v29pjhvkgpmhjm0000gn/T/',   Apple_PubSub_Socket_Render: '/private/tmp/com.apple.launchd.7Ax4C1EWMx/Render',   TERM_PROGRAM_VERSION: '404',   TERM_SESSION_ID: '82E05668-442D-4180-ADA3-8CF64D85E5A9',   USER: 'tugenhua',   SSH_AUTH_SOCK: '/private/tmp/com.apple.launchd.MYOMheYcL3/Listeners',   PATH: '/Users/tugenhua/.nvm/versions/node/v4.4.4/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin',   PWD: '/Users/tugenhua/个人demo',   LANG: 'zh_CN.UTF-8',   XPC_FLAGS: '0x0',   XPC_SERVICE_NAME: '0',   SHLVL: '1',   HOME: '/Users/tugenhua',   LOGNAME: 'tugenhua',   SECURITYSESSIONID: '186a8',   OLDPWD: '/Users/tugenhua/工作文档/sns_pc',   ZSH: '/Users/tugenhua/.oh-my-zsh',   PAGER: 'less',   LESS: '-R',   LC_CTYPE: 'zh_CN.UTF-8',   LSCOLORS: 'Gxfxcxdxbxegedabagacad',   NVM_DIR: '/Users/tugenhua/.nvm',   NVM_NODEJS_ORG_MIRROR: 'https://nodejs.org/dist',   NVM_IOJS_ORG_MIRROR: 'https://iojs.org/dist',   NVM_RC_VERSION: '',   MANPATH: '/Users/tugenhua/.nvm/versions/node/v4.4.4/share/man:/usr/local/share/man:/usr/share/man:/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/usr/share/man:/Applications/Xcode.app/Contents/Developer/usr/share/man:/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/share/man',   NVM_PATH: '/Users/tugenhua/.nvm/versions/node/v4.4.4/lib/node',   NVM_BIN: '/Users/tugenhua/.nvm/versions/node/v4.4.4/bin',   _: '/Users/tugenhua/.nvm/versions/node/v4.4.4/bin/node',   __CF_USER_TEXT_ENCODING: '0x1F5:0x19:0x34' }, pid: 14034, features:   { debug: false,   uv: true,   ipv6: true,   tls_npn: true,   tls_sni: true,   tls_ocsp: true,   tls: true }, _needImmediateCallback: false, config: {}, nextTick: [Function: nextTick], _tickCallback: [Function: _tickCallback], _tickDomainCallback: [Function: _tickDomainCallback], stdout: [Getter], stderr: [Getter], stdin: [Getter], openStdin: [Function], exit: [Function], kill: [Function], mainModule:   Module {   id: '.',   exports: {},   parent: null,   filename: '/Users/tugenhua/个人demo/process.js',   loaded: false,   children: [],   paths:    [ '/Users/tugenhua/个人demo/node_modules',    '/Users/tugenhua/node_modules',    '/Users/node_modules',    '/node_modules' ] } }