DSA using JavaScript

Stack

class Stack {
    constructor() {
        this.items = [];
    }

    push(element) {
        this.items.push(element);
    }

    pop() {
        if (this.isEmpty()) return null;
        return this.items.pop();
    }

    peek() {
        if (this.isEmpty()) return null; // Add null check for empty stack
        return this.items[this.items.length - 1];
    }

    isEmpty() {
        return this.items.length === 0;
    }

    size() { // Add size method to get stack length
        return this.items.length;
    }

    clear() { // Add clear method to empty the stack
        this.items = [];
    }
}

const stack = new Stack();  

// 1. Push Operation
console.log("\n--- Push Operations ---");
stack.push(10);
stack.push(20);
stack.push(30);
console.log("Stack after pushing 10, 20, 30:", stack.items); // [10, 20, 30]

// 2. Pop Operation
console.log("\n--- Pop Operations ---");
console.log("Popped item:", stack.pop()); // 30
console.log("Stack after pop:", stack.items); // [10, 20]

// 3. Peek Operation
console.log("\n--- Peek Operation ---");
console.log("Top element:", stack.peek()); // 20
console.log("Stack remains unchanged:", stack.items); // [10, 20]

// 4. isEmpty Operation
console.log("\n--- isEmpty Operation ---");
console.log("Is stack empty?", stack.isEmpty()); // false
const emptyStack = new Stack();
console.log("Is new stack empty?", emptyStack.isEmpty()); // true

// 5. Size Operation
console.log("\n--- Size Operation ---");
console.log("Stack size:", stack.size()); // 2

// 6. Clear Operation
console.log("\n--- Clear Operation ---");
stack.clear();
console.log("Stack after clear:", stack.items); // []
console.log("Is stack empty after clear?", stack.isEmpty()); // true

// Additional Examples showing error handling
console.log("\n--- Error Handling Examples ---");
const newStack = new Stack();
console.log("Pop from empty stack:", newStack.pop()); // null
console.log("Peek at empty stack:", newStack.peek()); // null

// Complex Example
console.log("\n--- Complex Example ---");
newStack.push("First");
newStack.push("Second");
newStack.push("Third");
console.log("Original stack:", newStack.items); // ["First", "Second", "Third"]
console.log("Size:", newStack.size()); // 3
console.log("Popped:", newStack.pop()); // "Third"
console.log("New top element:", newStack.peek()); // "Second"
console.log("Final stack:", newStack.items); // ["First", "Second"]