SOURCE

function Person (name, age, sex) {
    this.name = name;
    this.age = age;
    this.sex = sex;
}
function Student (name, age, sex, tel, grade) {
    // var this = {name:', age: ,sex: }
    Person.call(this, name, age, sex);
    this.tel = tel;
    this.grade = grade;
}
var student = new Student('SB', 18, 'male', 123, 2017);
console.log(student)