Node.js 開發環境與生產環境的區別

You can have different configurations for production and development environments.

Node.js assumes it's always running in a development environment. You can signal Node.js that you are running in production by setting theNODE_ENV=production

This is usually done by executing the command

export NODE_ENV=production

in the shell, but it's better to put it in your shell configuration file (e.g..bash_profilewith the Bash shell) because otherwise the setting does not persist in case of a system restart.

You can also apply the environment variable by prepending it to your application initialization command:

NODE_ENV=production node app.js

This environment variable is a convention that is widely used in external libraries as well.

Setting the environment toproductiongenerally ensures that

• logging is kept to a minimum, essential level
• more caching levels take place to optimize performance

For example Pug, the templating library used by Express, compiles in debug mode ifNODE_ENV

You can use conditional statements to execute code in different environments:

if (process.env.NODE_ENV === "development") {
  //...
}
if (process.env.NODE_ENV === "production") {
  //...
}
if(['production', 'staging'].indexOf(process.env.NODE_ENV) >= 0) {
  //...
})

For example, in an Express app, you can use this to set different error handlers per environment:

if (process.env.NODE_ENV === "development") {
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true }))
})

if (process.env.NODE_ENV === "production") {
  app.use(express.errorHandler())
})