My regex of choice is: /^[\+]?[(]?[0-9]{3}[)]?[-\s\.]?[0-9]{3}[-\s\.]?[0-9]{4,6}$/im Valid formats: (123) 456-7890 (123)456-7890 123-456-7890 123.456.7890 1234567890 +31636363634 075-63546725
function telephoneCheck(str) { var regex = /^(1\s?)?(\(\d{3}\)|\d{3})[\s\-]?\d{3}[\s\-]?\d{4}$/; return regex.test(str); }