Dynamic Prototype Pattern

Description

The dynamic prototype pattern encapsulates all of the information within the constructor by initializing the prototype if needed.

Example

function Person(name, age, job){/*from   w  w w  . j ava2s  .  co m*/
   //properties
   this.name = name;
   this.age = age;
   this.job = job;
   //methods
   if (typeof this.sayName != "function"){
      Person.prototype.sayName = function(){
          console.log(this.name);
      };
      Person.prototype.printAge = function(){
          console.log(this.age);
      };      
    }
}
var friend = new Person("XML", 29, "mark up");
friend.sayName();
friend.printAge();

The constructor adds the sayName() method if it doesn't already exist.

This block of code is executed only the first time the constructor is called.

The if statement may check for any property or method that will be present once initialized, there's no need for multiple if statements to check each property or method.

The code above generates the following result.