Whether an environment variable's value is contained within an allow list. Allow list is provided by a comma-separated environment variable value.
npm install env-allowed   
> Whether an environment variable's value is contained within an allow list. Allow list is provided by a comma-separated environment variable value.
$ npm install env-allowed --save
###### Start node or your program with a value that is in the allow list.
NODE_ENV=developent node
###### Create a comma-separated allow list.
process.env.ENVIRONMENTS = 'development,test';
###### Validate that the current NODE_ENV is within the allow list.
allowed('ENVIRONMENTS');
// true