Question

I am trying to write javascript code for making sure a field in my form has its first 2 characters as alphabets (US) and the rest 8 are numerics.

The total has to be 10, and if any of these are not satisfied, I should throw up an alert box.

I am checking for numerics now but I don’t know how to combine checking for alphabets and numerics in the same field.

Here is my code for checking for numerics.

Please help me out! sid is my field name.

// only allow numbers to be entered
var checkOK = "0123456789";
var checkStr = document.forms[0].sid.value;
var allValid = true;
var allNum = "";

for (i = 0; i < checkStr.length; i++)
{
    ch = checkStr.charAt(i);
    for (j = 0; j < checkOK.length; j++)
        if (ch == checkOK.charAt(j))
            break;

    if (j == checkOK.length)
    {
        allValid = false;
        break;
        if (ch != ",")
            allNum += ch;
    }
    if (!allValid)
    {
        alert("Please enter only 8 numeric characters in the \"sid\" field.");
        return (false);
    }
}    

Answer 1

A single regular expression will easily perform this check :

   /^[a-zA-Z]{2}\d{8}$/

/^ match beginning of string

[a-zA-Z]{2} match exactly 2 alphabetic characters

\d{8} match exactly 8 digits

$/ match end of string

Use as follows :

 /^[a-zA-Z]{2}\d{8}$/.test (str)   // Returns true or false