phone-number.jl

isfrom2to9(n) = n != '0' && n != '1'

function clean(phone_number)
    filtered = filter(isnumeric, phone_number)
    n = length(filtered)
    if n == 11
        filtered[1] != '1' && return nothing
        filtered = filtered[2:end]
        n = 10
    end
    if n == 10
        if !isfrom2to9(filtered[1]) || !isfrom2to9(filtered[4])
            return nothing
        else
            return filtered
        end
    end
    nothing
end