Stack: Array as Storage

Before writing this, I had a serious debate with myself. Is there a need to implement your own stack using arrays in JavaScript, when the the language itself provides methods, pop() and push(), which are needed in a typical stack???

For the sake of understanding stacks better, I ended up implementing my own, assuming that my stack grows dynamically.

Implementation

1.Create a stack class

class Stack {
    constructor() {
        this.items = [];
        this.size = -1;
    }
//add methods
}

In our stack class, we declare an array to implement a stack and set the size to -1 (empty).

2.Add methods to stack class to perform push, pop, peek.

push item to stack

push(data) {
        //if an item is provided
        if (data) {
            //add item to array
            this.items.push(data);
            //increase size
            this.size++;
        }
        return;        
    }

Here, an item is added to top of stack.

pop item in stack
The top item in stack is removed and returned. If list is empty Underflow is returned.

pop() {
    //if empty
    if (this.size === -1) {
      return "UnderFlow";
    } else {
        this.size--;
        //return top item in stack
      return this.items.pop();
    }
  }

peek
Returns top element but does not remove it from stack

 peek() {
    //if empty
    if (this.size === -1) {
      return "Empty stack";
    }
    //return top item in stack
    return this.items[this.size];
  }

Example Test Code

let stack = new Stack();
stack.push(3);
stack.push(5);
stack.push(7);
console.log(stack.pop());//7
console.log(stack.peek());//5
console.log(stack)//[3, 5]

Next, I'll be applying my stack knowledge in creating a postfix calculator 😉 .
Happy coding.