How to implement array object - JavaScript

In this article we will learn how to implementing array Data Structure in Javascript.

An Array is a simple data Structure, in which elements are stored in contiguous memory locations.

Create a skeleton of a array class

Skeleton of a array class

class Array {

    constructor() {

        // length of array.
        this.length = 0;
         
        // Object to store elements.
        this.data = {};
    }


    // Methods to implement
    // push
    // pop
    // insertAt()
    // deleteAt()
    // getElementAtIndex()
}

Now we have created a skeleton for the class, and when that class is called, we can access the methods and properties of that class, like this:

const array = new Array();

But we didn't create any properties or methods for that class, we just did a skeleton, so if we print that class we won't find anything in it.

const array = new Array();

console.log(array);
// Array { length: 0, data: {} }

Now let’s see implementation of each method:

Implementation of push method

This function is used to push an element at the end of the array.

Implementation

class Array {
    constructor() {

        // length of array.
        this.length = 0;
         
        // Object to store elements.
        this.data = {};
    }

    // Push element into array
    push(element) {
        this.data[this.length] = element;
        console.log('Inserted', this.data[this.length]);
        this.length++;
        return this.data;
    }
}

Now that we've done the implementation, let's do a test for the array class.

// Create an array class
const array = new Array();

// Push new element
console.log(array.push('Mohamed'));

Output

Inserted Mohamed
{ '0': 'Mohamed' }

Implementation of pop method

pop is used to delete an element at the end of the array.

Implementation

pop() {
    let item = this.data[this.length - 1];
    delete this.data[this.length - 1];
    console.log('Deleted', item);
    this.length--;
    return this.data;
}

Now that we've done the implementation, let's do a test for the array class.

// Create an array class
const array = new Array();

// Push element
console.log(array.push('Mohamed'));

// Delete element
console.log(array.pop());

Output

Inserted Mohamed
{ '0': 'Mohamed' }
Deleted Mohamed
{}

Implementation of insertAt method

This function is used to insert an element at the given index.

Implementation

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;
}

Now that we've done the implementation, let's do a test for the array class.

// Array
const array = new Array();

// Push elements
array.push('John');
array.push('Doe');

// Print the array
console.log(array);

// `insertAt` index 1
array.insertAt('John', 1);

// Print the array
console.log(array);

Output

Inserted John
Inserted Doe
Array { length: 2, data: { '0': 'John', '1': 'Doe' } }
Array { length: 3, data: { '0': 'John', '1': 'John', '2': 'Doe' } }

Implementation of deleteAt method

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

Implementation

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;
}

Now that we've done the implementation, let's do a test for the array class.

// Array
const array = new Array();

// Push elements
array.push('John');
array.push('Doe');

// Print the array
console.log(array);

// Insert
array.insertAt('John', 1);

// Delete
array.deleteAt(1);

// Print the array
console.log(array);

Output

Inserted John
Inserted Doe
Array { length: 2, data: { '0': 'John', '1': 'Doe' } }
Array { length: 2, data: { '0': 'John', '1': 'Doe' } }

Full code:

class Array {
    constructor() {

        // length of array.
        this.length = 0;

        // Object to store elements.
        this.data = {};
    }

    // For push new element
    push(element) {
        this.data[this.length] = element;
        console.log('Inserted', this.data[this.length]);
        this.length++;
        return this.data;
    }

    // Delete last element of array
    pop() {
        let item = this.data[this.length - 1];
        delete this.data[this.length - 1];
        console.log('Deleted', item);
        this.length--;
        return this.data;
    }

    // Insert at a specific 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;
    }

    // delete from a specific index
    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;
    }
}

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