What is NODE ENV and how to use it in Express

Question

This is my the app  I m currently running on production   var app   express    app set  views  settings c WEB PATH     public templates    app set  view engine   ejs    app configure function        app use express favicon         app use express static settings c WEB PATH     public         app use express bodyParser         app use express cookieParser         app use express methodOverride         app use express session               cookie   domain     settings c SITE DOMAIN  maxAge 1440009999               secret  hamster               store  r store                       app use useragent express         app use flash         app use passport initialize         app use passport session           However  I came to know about NODE ENV and want to use it  How can I do this

User · Answer

NODE ENV is an environmental variable that stands for node environment in express server   It s how we set and detect which environment we are in   It s very common using production and development   Set   export NODE ENV production   Get   You can get it using app get  env

User · Answer

Typically  you d use the NODE ENV variable to take special actions when you develop  test and debug your code  For example to produce detailed logging and debug output which you don t want in production  Express itself behaves differently depending on whether NODE ENV is set to production or not  You can see this if you put these lines in an Express app  and then make a HTTP GET request to  error  app get   error   function req  res      if   production      app get  env          console log  quot Forcing an error  quot          throw new Error  TestError         app use function  req  res  next      res status 501  send  quot Error  quot       Note that the latter app use   must be last  after all other method handlers  If you set NODE ENV to production before you start your server  and then send a GET  error request to it  you should not see the text Forcing an error  in the console  and the response should not contain a stack trace in the HTML body  which origins from Express   If  instead  you set NODE ENV to something else before starting your server  the opposite should happen  In Linux  set the environment variable NODE ENV like this   export NODE ENV  value

User · Answer

NODE ENV is an environment variable made popular by the express web server framework  When a node application is run  it can check the value of the environment variable and do different things based on the value  NODE ENV specifically is used  by convention  to state whether a particular environment is a production or a development environment  A common use-case is running additional debugging or logging code if running in a development environment  Accessing NODE ENV You can use the following code to access the environment variable yourself so that you can perform your own checks and logic  var environment   process env NODE ENV  Assume production if you don t recognise the value  var isDevelopment   environment      development   if  isDevelopment      setUpMoreVerboseLogging      You can alternatively using express  app get  env   function  but note that this is NOT RECOMMENDED as it defaults to  quot development quot   which may result in development code being accidentally run in a production environment - it s much safer if your app throws an error if this important value is not set  or if preferred  defaults to production logic as above   Be aware that if you haven t explicitly set NODE ENV for your environment  it will be undefined if you access it from process env  there is no default  Setting NODE ENV How to actually set the environment variable varies from operating system to operating system  and also depends on your user setup  If you want to set the environment variable as a one-off  you can do so from the command line   linux  amp  mac  export NODE ENV production windows   env NODE ENV    production   In the long term  you should persist this so that it isn t unset if you reboot - rather than list all the possible methods to do this  I ll let you search how to do that yourself  Convention has dictated that there are two  main  values you should use for NODE ENV  either production or development  all lowercase  There s nothing to stop you from using other values   test  for example  if you wish to use some different logic when running automated tests   but be aware that if you are using third-party modules  they may explicitly compare with  production  or  development  to determine what to do  so there may be side effects that aren t immediately obvious  Finally  note that it s a really bad idea to try to set NODE ENV from within a node application itself - if you do  it will only be applied to the process from which it was set  so things probably won t work like you d expect them to  Don t do it - you ll regret it

User · Answer

I assume the original question included how does Express use this environment variable   Express uses NODE ENV to alter its own default behavior   For example  in development mode  the default error handler will send back a stacktrace to the browser   In production mode  the response is simply Internal Server Error  to avoid leaking implementation details to the world

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