check_valid_number.js

self.check_valid_number = function(input){
    // an attempt to solve the insanity of JavaScript numbers
    var numbers_only = new RegExp('^\\d+$');
    if (input !== '' && numbers_only.test(input) && !Number.isNaN(Number(input))){
        return true;
    } else {
        return false;
    }
};

self.check_number_in_range = function(input, start, end){
    return self.check_valid_number(input) && (parseInt(input) >= start) && (parseInt(input) <= end);
}