JavaScript注册表格中用于传真号码验证的正则表达式

Question

I am a complete newbie when it comes to regular expressions. Even after reading guides about them, I still have a hard time formulating my own. I am trying to get my form to validate the fax number in the +12345678910 format. I have some code, but it allows me to submit mixed numbers and letters, as well as submit data with blank spaces and without filling out the faxnum text box completely. I would strongly appreciate any help with the form and tips on how to become more proficient with regex.

var fax = document.registration.faxnum; 
faxval(fax);

function faxval(fax)
{
    var numbers = /[\+? *[1-9]+]?[0-9 ]+/; //Bad regex
    if (fax.value.match(numbers))
    {
        document.getElementById("faxmsg").innerHTML=("Everything is OK.");
        faxmsg.style.color="green";
    }
    else
    {
        faxmsg.innerHTML=("Invalid fax number.");
        faxmsg.style.color="red";
    }
};

Answer 1

To match a number like +12345678910, try: \\+1[2-9][0-9]{9}

I assume that the +1 portion is the international number code, 234 is the area code, 567 is the exchange and 8910 is the rest of the number. This pattern would also match a number such as +12125551212.

The first digit of any US or Canadian phone number must be 2 through 9. So we can allow that as the first character ( [2-9] ). Then the rest of the number will be 9 digits long, 0 through 9 ( [0-9]{9} ).

If you want to allow - or . too, you can use: \\+1(|\\.|\\-)[2-9][0-9]{2}(|\\.|\\-)[0-9]{3}(|\\.|\\-)[0-9]{4} . The (|\\.|\\-) part means "allow no character OR a . character OR a - character."