CODE EXAMPLE FOR JAVASCRIPT

stack implementation in javascript using array

class Stack{
    constructor(){
        this.array = [];
        this.count = 0;
    }

    isEmpty(){
        return this.count == 0;
    }

    size(){
        return this.count;
    }

    peekTop() {
        if(this.count == 0){
            return "Stack is Empty";
        }
        return this.array[this.count-1];
    }

    peek(pos){
        var top =this.count-1;
        if(top-pos+1<0)
            return "invalid index";
        else
            return this.array[top-pos+1];
    }

    push(data){
        this.count++;
        this.array.push(data);
    }

    pop(){
        if(this.array.length == 0)
            return "Stack is Underflow";
        this.count--;
        return this.array.pop();
    }

    print(){
        if(this.count == 0){
            return "Unable to Print,Stack is Empty :-(";
        }
        var str = "";
        for (var i = this.array.length-1; i >= 0; i--)
            str += this.array[i] + " ";
        return str;
    }
}

const arrStack = new Stack();
arrStack.push("10");
arrStack.push("20");
arrStack.push("30");
arrStack.push("40");
console.log("Peek Top element is ",arrStack.peekTop());
arrStack.push("50");
console.log("Poped element in stack ",arrStack.pop());
console.log("Peeked element at position 2",arrStack.peek(2));
console.log("element in stack
",arrStack.print());
console.log("is Stack empty? ",arrStack.isEmpty());
console.log("Size of stack is ",arrStack.size());

/**
 * Time Complexity -> O(1) (all opeartion take constant time)
 * Space Complexity -> O(1)
 */