Good Day.

I am using the following code to validate data on a HTML page

function checkTermMoYr (strng) {
 var error = "";
 if (strng == "") {
    error = "You didn't enter a Loan Term.\n";
 }
//var illegalChars = /\W/;
var illegalChars = \s;
  // allow only letters, numbers, and underscores
    if (illegalChars.test(strng)) {
       error = "The Loan Term contains illegal characters.\n";
    }
   return error
   }

What I can't figure out is how to allow only letters, numbers and spaces. Any help is greatly appreciated.