Sample 1

        var Employee = function (firstName, lastName, gender, email) {
            this.firstName = firstName;
            this.lastName = lastName;
            this.gender = gender;
            this.email = email;
        };

        Employee.prototype.getFullName = function () {
            return this.firstName + " " + this.lastName;
        };

        Employee.prototype.getEmail = function () {
            return this.email;
        };

        Employee.prototype.getGender = function () {
            return this.gender;
        };

        var employee1 = new Employee("Mark", "Matt", "Male", "a@a.com");

        // output 1a
        for (let property in employee1) {
            document.getElementById('output1a').innerHTML += '    ' + property + '\n';
        }

        // output 1b (filter with `hasOwnProperty()` check)
        for (let property in employee1) {
            if(employee1.hasOwnProperty(property)) {
                document.getElementById('output1b').innerHTML += '    ' + property + '\n';
            }
        }
    

Output 1a

    firstName
    lastName
    gender
    email
    getFullName
    getEmail
    getGender

Output 1b

    firstName
    lastName
    gender
    email