Separate Code from Data

A principle in DOP. Seperate code from data in a way that the code resides in functions whose behavior does not depend on data encapsulated in the function’s context

Example in OOP

Original:

class Author {
  constructor(firstName, lastName, books) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.books = books;
  }
  fullName() {
    return this.firstName + " " + this.lastName;
  }
  isProlific() {
    return this.books > 100;
  }
}
 
var obj = new Author("Isaac", "Asimov", 500); // (1)
obj.fullName();

DOP revisions:

class AuthorData {
  constructor(firstName, lastName, books) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.books = books;
  }
}
 
class NameCalculation {
  static fullName(data) {
    return data.firstName + " " + data.lastName;
  }
}
 
class AuthorRating {
  static isProlific (data) {
    return data.books > 100;
  }
}
 
var data = new AuthorData("Isaac", "Asimov", 500); 
NameCalculation.fullName(data);