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JavaScript Design Patterns for Coding Interviews

Challenge: Solution Review

Explore how to implement and use a ReverseIterator class to traverse JavaScript hashmaps in reverse order. Learn essential behavioral pattern methods like hasprevElement, last, and previous to manage object communication effectively. Understand this solution to apply design patterns during interview challenges.

We'll cover the following...

Solution #

Node.js
class ReverseIterator {
  constructor(elements) {
	    this.keys = Object.keys(elements)
      this.index = this.keys.length - 1
      this.elements = elements
   }
  hasprevElement() {
    return this.index >=0
  }
  last(){
	  this.index = this.keys.length - 1 
	  return this.elements[this.keys[this.index]]
  }
  previous(){
    if(this.index >= 0){
      return  this.elements[this.keys[--this.index]]	  	
    }else{
      return null
    }
	
  }
}
function reverseIterate(items){
    var iter = new ReverseIterator(items)
    
    for(var i = iter.last();iter.hasprevElement(); i = iter.previous()){
		  console.log(i)
    }	    
}
reverseIterate({'name': 'Anne', 'age': '23', 'gender': 'Female', 'Occupation': 'Engineer'})

Explanation

In the code above, we defined a ReverseIterator class that initializes the following properties:

  • keys: all the keys of the hashmap are accessed using Object.keys and stored in this property

  • index: keeps track of keys in the hashmap

  • elements: stores the hashmap ...