2023年7月7日发(作者：)

【node】express的⽂件⾥⾯的问题描述在分析⾥⾯的代码的时候，有：var port = normalizePort( || '3001');('port', port);产⽣两个疑问：这⾥为什么不直接设

(‘port’,‘3001’)

?是什么？问题解疑是环境变量在node中，有全局变量process表⽰的是当前的node进程。包含着关于系统环境的信息。但是中并不存在PORT这个变量。PORT是⽤户⼀个⾃定义的变量。我们可以通过以下代码，来查看process的值：(process);输出结果为：$ node ess { 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: '/download/release/v4.4.4/', headersUrl: '/download/release/v4.4.4/' }, argv:

[ '/Users/tugenhua/.nvm/versions/node/v4.4.4/bin/node', '/Users/tugenhua/个⼈demo/' ], execArgv: [], env:

{ TERM_PROGRAM: 'Apple_Terminal', SHELL: '/bin/zsh', TERM: 'xterm-256color', TMPDIR: '/var/folders/l7/zndlx1qs05v29pjhvkgpmhjm0000gn/T/', Apple_PubSub_Socket_Render: '/private/tmp/d.7Ax4C1EWMx/Render', TERM_PROGRAM_VERSION: '404', TERM_SESSION_ID: '82E05668-442D-4180-ADA3-8CF64D85E5A9', TERM_SESSION_ID: '82E05668-442D-4180-ADA3-8CF64D85E5A9', USER: 'tugenhua', SSH_AUTH_SOCK: '/private/tmp/YcL3/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_-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_-8', LSCOLORS: 'Gxfxcxdxbxegedabagacad', NVM_DIR: '/Users/tugenhua/.nvm', NVM_NODEJS_ORG_MIRROR: '/dist', NVM_IOJS_ORG_MIRROR: '/dist', NVM_RC_VERSION: '', MANPATH: '/Users/tugenhua/.nvm/versions/node/v4.4.4/share/man:/usr/local/share/man:/usr/share/man:/Applications//Contents/Developer/Platforms/rm/Developer/SDKs//usr/share/man:/Applications//Contents/Developer/usr/share/man:/Applications//Contents/Developer/Toolchains/chain/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/', loaded: false, children: [], paths:

[ '/Users/tugenhua/个⼈demo/node_modules', '/Users/tugenhua/node_modules', '/Users/node_modules', '/node_modules' ] } }我们可以看到在env这个变量⾥⾯，没有PORT变量。所以对于代码：var port = normalizePort( || '3001');('port', port);是先考虑到node的进程的环境变量的端⼝，再考虑3001端⼝号。