JAVASCRIPT

set NODE_ENV

SET NODE_ENV=development

set node_env in windows

cross-env NODE_ENV=production my-command

set NODE_ENV

export NODE_ENV=development

NODE_ENV

//Before running your app, you can do this in console:

//OS X
export NODE_ENV=production

//Win
SET NODE_ENV=production

//PowerShell
$env:NODE_ENV="production"

//or you can run your app like this:
NODE_ENV=production node app.js

//You can also set it in your js file:
process.env.NODE_ENV = 'production';