Ternary operator not behaving as intended - node.js

Question

my Code link
on line currentEnvironment = typeof (process.env.NODE_ENV === 'string') ? currentEnvironment.toLowerCase() : '';
when I pass the input 🌈 uptime-monitoring-app >> NODE_ENV=production node app.js it works without any issue.
Command Line arguments :
0: /usr/local/Cellar/node#10/10.15.0/bin/node
1: /Users/tentacion/Documents/CODE/Node without NPM/uptime-monitoring-app/app.js
string
Server Started # 5000 Environment : production
--------------------------------------------------------------------------------------------------
BUT for the input uptime-monitoring-app >> Nnode app.js it throws error, because now the NODE_ENV variable is undefined now.
Command Line arguments :
0: /usr/local/Cellar/node#10/10.15.0/bin/node
1: /Users/tentacion/Documents/CODE/Node without NPM/uptime-monitoring-app/app.js
undefined
/Users/tentacion/Documents/CODE/Node without NPM/uptime-monitoring-app/envConfig.js:66
currentEnvironment = typeof (process.env.NODE_ENV === 'string') ? currentEnvironment.toLowerCase() : '';
^
TypeError: Cannot read property 'toLowerCase' of undefined
at Object.<anonymous> (/Users/tentacion/Documents/CODE/Node without NPM/uptime-monitoring-app/envConfig.js:66:86)
at Module._compile (internal/modules/cjs/loader.js:689:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
at Module.load (internal/modules/cjs/loader.js:599:32)
at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
at Function.Module._load (internal/modules/cjs/loader.js:530:3)
at Module.require (internal/modules/cjs/loader.js:637:17)
at require (internal/modules/cjs/helpers.js:22:18)
at Object.<anonymous> (/Users/tentacion/Documents/CODE/Node without NPM/uptime-monitoring-app/app.js:11:19)
at Module._compile (internal/modules/cjs/loader.js:689:30)
🌈 uptime-monitoring-app >>
What I expected
if the NODE_ENV variable is undefined then the expression typeof (process.env.NODE_ENV === 'string') would be false so the next statement should be executed. ie assigning it with the empty string.
Please help, I don't know what am I doing wrong. I am new to node

Answer 1

process.env.XXX are always either a string or undefined.
Prefer something like const { XXX = 'some-default-value' } = process.env, which is called object destructuring, which will either use the provided value for XXX or give it a default value if it is undefined.