requiredfield example

gistfile1.js

var requeiredFieldOptions = {
    watermarkText: "Enter age here...",
    functionValidate: function(value) {
        if (parseInt(value) < 18) {
            return false;
        }
        return true;
    },
    dataType: "number",
    liveCheck: true
};

$("#requeiredField").requiredfield(requeiredFieldOptions);

// jsfiddle: http://jsfiddle.net/acatl/Lh99C/