What phone validation algorithm do you use for the International Project?

Question

Validation

Often there is a problem in checking the validity of the phone entered on the site. Checking via SMS is not economically budgetary to do. Share the verification algorithms at the level of the entered data, which takes into account: the minimum number of characters; block to format numbers 123456789 and so on

Answer 1

https://github.com/jackocnr/intl-tel-input
Mask for international numbers. Of course, it won't work 100%.