Ha, good to see this here - so incredibly useful, and already ported to lots of useful languages. Handling phone numbers gets messy really quickly: formatting/validation for national/international numbers, in different forms (land-line/mobile/premium etc), in hundreds of different countries... These guys have done a great job, and are also super responsive/helpful when you raise issues.
A word of warning: if you ever set out to handle international numbers in a web frontend - you may think "it can't be that hard - maybe take me a couple of hours" (like me), then do yourself a favour and save yourself a week of unexpected work and use the jQuery plugin that I ended up creating (I don't understand why this didn't already exist) which uses libphonenumber for all the magic: https://github.com/Bluefieldscom/intl-tel-input. Hope it saves you some time.