TypeScript: Modern JavaScript Development

Chapter 3. Creational Design Patterns

Creational design patterns in object-oriented programming are design patterns that are to be applied during the instantiation of objects. In this chapter, we'll be talking about patterns in this category.

Consider we are building a rocket, which has payload and one or more stages:

class Payload { 
  weight: number; 
} 
 
class Engine { 
  thrust: number; 
} 
 
class Stage { 
  engines: Engine[]; 
} 

In old-fashioned JavaScript, there are two major approaches to building such a rocket:

• Constructor with new operator
• Factory function

For the first approach, things could be like this:

function Rocket() { 
  this.payload = { 
    name: 'cargo ship' 
  }; 
   
  this.stages = [ 
    { 
      engines: [ 
        // ... 
      ] 
    } 
  ]; 
} 
 
var rocket = new Rocket(); 

And for the second approach, ...