Validate phone number with JavaScript

Question

I found this code in some website, and it works perfectly. It validates that the phone number is in one of these formats:
(123) 456-7890 or 123-

Answer 1

/^[+]*[(]{0,1}[0-9]{1,3}[)]{0,1}[-\s\./0-9]*$/g

(123) 456-7890
+(123) 456-7890
+(123)-456-7890
+(123) - 456-7890
+(123) - 456-78-90
123-456-7890
123.456.7890
1234567890
+31636363634
075-63546725

This is a very loose option and I prefer to keep it this way, mostly I use it in registration forms where the users need to add their phone number. Usually users have trouble with forms that enforce strict formatting rules, I prefer user to fill in the number and the format it in the display or before saving it to the database. http://regexr.com/3c53v