EPP-style phone numbers use the format +CCC.NNNNNNNNNNxEEEE, where C is the 1–3 digit country code, N is up to 14 digits, and E is the (optional) extension. The leading plus sign and the dot following the country code are required.

The literal “x” character is … The literal “x” character is required only if an extension is provided. where C is the 1–3 digit country code, N is up to 14 digits, and E is the (optional) extension. The leading plus sign and the dot following the country code are required. Phone number must start with '+' or '00' for an international call.

Regular Expression (Regex) for Phone Numbers – International and U.S. Formats I have been looking all over the web for a regular expression to use in JavaScript functions to help with formatting phone number links and printing phone numbers on …