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JavaScript Design Patterns for Coding Interviews

Challenge: Solution Review

Explore how the chain of responsibility behavioral pattern assigns tasks based on employee skill levels. Learn to implement handler classes, set up a chain, and forward requests in JavaScript to manage work delegation efficiently.

We'll cover the following...

Solution #

Node.js
class EmployeeChain 
{
  setNext(nextInChain){}
  assignWork(req){}
} 
  
class Employee
{
  constructor(name,level){
    this.name = name
    this.level = level
  }
  
  getLevel(){ 
    return this.level
  } 
  getName(){
    return this.name
  }
  
} 
  
class EasyLevelWorkHandler extends EmployeeChain
{
  constructor(){
    super()
    this.nextInChain = new EmployeeChain()
  } 
  
  setNext(nextObj){ 
    this.nextInChain = nextObj; 
  } 
  
  assignWork(req) { 
    if (req.getLevel() == "Easy") { 
      console.log("Easy work assigned to: " + req.getName()); 
    }else{ 
      this.nextInChain.assignWork(req); 
    } 
  } 
} 
  
class MediumLevelWorkHandler extends EmployeeChain
{ 
  constructor(){
    super()
    this.nextInChain = new EmployeeChain()
  } 
  
  setNext(nextObj){ 
    this.nextInChain = nextObj; 
  } 
  
  assignWork(req) { 
    if (req.getLevel() == "Medium") { 
      console.log("Medium work assigned to: " + req.getName()); 
    }else{ 
      this.nextInChain.assignWork(req); 
    } 
  } 
} 
class HardLevelWorkHandler extends EmployeeChain
{ 
  constructor(){
    super()
    this.nextInChain = new EmployeeChain()
  } 
  
  setNext(nextObj){ 
    this.nextInChain = nextObj; 
  } 
  
  assignWork(req) { 
    if (req.getLevel() == "Hard") { 
      console.log("Hard work assigned to: " + req.getName()); 
    }else{ 
      this.nextInChain.assignWork(req); 
    } 
  } 
} 
var w1 = new EasyLevelWorkHandler(); 
var w2 = new MediumLevelWorkHandler(); 
var w3 = new HardLevelWorkHandler(); 
w1.setNext(w2); 
w2.setNext(w3); 
 
const emp1 = new Employee("Joe","Easy")
const emp2 = new Employee("Anne","Medium")
const emp3 = new Employee("Shawn","Hard")
  
w1.assignWork(emp1); 
w1.assignWork(emp2); 
w1.assignWork(emp3);

Explanation

In this challenge, you had to use the chain of responsibility pattern to assign work to employees. We start by creating an employee. Here’s what the Employee class looks like:

class Employee
{
  constructor(name,level){
    this.name = name
    this.level = level
  }
  
  getLevel(){ 
    return this.level
  } 

  getName(){
    return this.name
  }
  
}

An employee will have a name and a level. Every employee can have one of the three levels: easy, medium, or hard. The level of an employee denotes the level of tasks that they can handle. So, an employee with an easy level can only handle easy tasks and the same goes for employees with medium and hard levels.

The getLevel and ...