Михаил

function getFIO(name, surname, patronymic){
  this.name = name;
  this.surname = surname;
  this.patronymic = patronymic;

  var that = this;

  this.sayHello = function() {
    console.log(`Меня зовут ${that.surname} ${that.name} ${that.patronymic}`);
  }
}

let cls = localStorage.getItem('body-class');

if (cls) {
  $("body").addClass(cls);
}

$(".btn").click(function(){
    $("body").addClass("active");
    localStorage.setItem('body-class', 'active');
});