Question

I’m having trouble trying to get JavaScript and Regex to recognize an input from an HTML file that I’m working on.

function validateSchoolClass(field)
{
if(field == "") 
{
    return "No class ID was entered.\n";
}
else if (field.length != 4)
{
    return "Class ID must be 4 characters.\n";
}
else if (/[^A-Z]{2}[^0-9]{2}/.test(field))
{
    return "Class Name must be two capital letters followed by two numbers.\n";
}
return "";
}

What I want to happen is that input into the field that is passed will contain 4 characters the first 2 will be capital letters and the next 2 will be numbers. I don’t know if I’m missing something but from everything that I have read this should work, but it doesn’t and any 4 character input that is passed still counts as being valid!

Answer 1

I’d change that final else if to

else if (!/^[A-Z]{2}[0-9]{2}$/.test(field))

That regular expression tests for two capital letters followed by two digits, and then I use the ! to invert the result, so you can report things that don’t match. (I also added anchors at the beginning and end, but with your earlier length check, they’re probably technically superfluous.)