what is the use of get and set in javascript code example

Example 1: getters and setters javascript

let obj = {
  log: ['a', 'b', 'c'],
  get latest() {
    if (this.log.length === 0) {
      return undefined;
    }
    return this.log[this.log.length - 1];
  }
};

obj.log.push('d');
console.log(obj.latest); //output: 'd'

Example 2: javascript getters and setters

/*Getter functions are meant to simply return (get) the value of an object's 
private variable to the user without the user directly accessing the private 
variable.*/
/*Setter functions are meant to modify (set) the value of an object's private 
variable based on the value passed into the setter function. This change could
involve calculations, or even overwriting the previous value completely.*/
class Book {
  constructor(author) {
    this._author = author;
  }
  // getter
  get writer() {
    return this._author;
  }
  // setter
  set writer(updatedAuthor) {
    this._author = updatedAuthor;
  }
}
const novel = new Book('anonymous');
console.log(novel.writer);  // anonymous
novel.writer = 'newAuthor';
console.log(novel.writer);  // newAuthor

Example 3: getter and setters in js

var person={firstname:"chetha",secondname="kumar",get fullname()
{
  	return this.firstname+" "+this.secondname;
}
document.write(person.fullname);
var person={firstname:"chethan",secondname="kumar",course:"",set course(x)
{
  	this.course=x;
}
person.course="bca";
document.write(person.course);