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Implementation of Array class in JavaScript
  • Last Updated : 27 Feb, 2019

This article implementing Arrays using JavaScript. An Array is a simple data Structure, in which elements are stored in contiguous memory locations. Implementation of arrays performs various operations like push (adding element), pop (deleting element) element at the end of the array, getting the element from particular index, inserting and deleting element from particular index.

Array class in JavaScript:




// User defined class Array
class Array {
  
    // Create constructor
    constructor() {  
      
        // It store the length of array.
        this.length = 0; 
          
        // Object to store elements.
        this.data = {}; 
    }
}

In the above example, create a class Array which contains two properties i.e. length and data, where length will store the length of an array and data is an object which is used to store elements.

Function in Array: There are many functions in array which are listed below:

  • Push()
  • Pop()
  • insertAt()
  • deleteAt()
  • getElementAtIndex()

Push(element): This function is used to push an element at the end of the array.






push(element) {
    this.data[this.length] = element;
    this.length++;
    return this.data;
}

Pop(): It is used to delete an element at the end of the array.




pop() {
    let item = this.data[this.length-1];
    delete this.data[this.length-1];
    this.length--;
    return this.data;
}

In the above example, item variable will store the last element from data object and perform deletion of last element and then, it will decrease the length of by 1 and return the object.

insertAt(): This function is used to insert an element at given index.




insertAt(item, index) {
    for(let i=this.length;i>=index;i--) {
      this.data[i]=this.data[i-1];
    }
    this.data[index]=item;
    this.length++; 
    return this.data;
}

This function accepts two parameters item and index. Index number denoting the place where data to be inserted and item is the value which is to be inserted at index.

deleteAt(index): This function is used to remove an element at given index or property in a data object.




deleteAt(index) {
    for(let i = index; i < this.length - 1; i++) {
      this.data[i] = this.data[i+1];
    }
    delete this.data[this.length-1];
    this.length--;
    return this.data;
}

In above function, use loop to reach at index till the end, and copy the next element at index and at the end of loop two copies of last element exist, delete last element through delete operator.

getElementAtIndex(index): It returns the element at given index.




getElementAtIndex(index) {
    return this.data[index];
}

Example: This function describes the implementation of array class and its various operations.




<!DOCTYPE html>
<html>
  
<head>
    <title>
        Implementation of array
    </title>
</head>
  
<body>
    <script>
        class Array{
      constructor(){
        this.length=0;
        this.data={};
      }
      getElementAtIndex(index){
        return this.data[index];
      }
      push(element){
        this.data[this.length]=element;
        this.length++;
        return this.length;
      }
      pop(){
        const item= this.data[this.length-1];
        delete this.data[this.length-1];
        this.length--;
        return this.data;
      }
      deleteAt(index){
        for(let i=index; i<this.length-1;i++){
          this.data[i]=this.data[i+1];
        }
        delete this.data[this.length-1];
        this.length--;
        return this.data;
      }
      insertAt(item, index){
        for(let i=this.length;i>=index;i--){
          this.data[i]=this.data[i-1];
        }
        this.data[index]=item;
        this.length++;
        return this.data;
      }
    }
    const array= new Array(); //we are instantiating an object of Array class
    array.push(12);
    array.push(13); //pushing element 
    array.push(14);
    array.push(10);
    array.push(989);
    document.write("<div>Print element in an array</div>");
    for(var key in array.data){
      document.write("<span>"+array.data[key]+" "+"</span>"); 
    }
      
      
    document.write("<div>Pop element in an array</div>");
    array.pop(); //Popping element 989
    for(var key in array.data){
      document.write("<span>"+array.data[key]+" "+"</span>"); 
    }
      
      
    document.write("<div>Inserting element at position 2</div>");
    array.insertAt(456, 2); //Inserting element 456
    for(var key in array.data){
      document.write("<span>"+array.data[key]+" "+"</span>"); 
    }
      
    document.write("<div>deleting element at position 3</div>");
    array.deleteAt(3); //Deleting 14
    for(var key in array.data){
      document.write("<span>"+array.data[key]+" "+"</span>"); 
    }
      
    document.write("<div>Getting  element at position 2</div>");
    document.write("<div>"+array.getElementAtIndex(2)+"</div>");
    </script>
</body>
</html>                    

Output:

full-stack-img

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