UnhandledPromiseRejectionWarning: MongoParseError: URI does not have hostname, domain name and tld code example

Example 1: UnhandledPromiseRejectionWarning: MongoParseError: URI does not have hostname, domain name and tld

Ensure special characters in your password are encoded. 
For example if your password contains '#' you should replace the literal '#' character with '%23' where 23 is the hex code for '#' 
see: https://docs.atlas.mongodb.com/troubleshoot-connection/#special-characters-in-connection-string-password

Example 2: MongoParseError: URI does not have hostname, domain name and tld

You should encode your password, for example, my password 
had # character in it
I used this site to convert # to hex which is 23
https://cryptii.com/pipes/hex-to-text
Now, after converting it you need to put it inside your js 
file like this %23