The two important parts of a stack data structure are the pop and push functions. Before you pop, you need to check whether the stack is empty. If it’s not empty you can remove and return the last element (the element that was added to the stack last). Remember to decrement the pointer (top) before you leave the function.

Similarly, before we conduct a push operation, we need to check whether the stack is full. If not we can insert the element at the end of the stack. Remember to increment the pointer (top) before exiting the function.

Finally, you can use the main function to call push and pop functions to examine the behavior of the stack we just created. Of course, you can improve this stack by including functions like peek, getSize, etc.

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class Stack {

  // Array is used to implement stack

  constructor() {

    this.items = [];

  }

​

  // Functions we'll need

  push(val) {

    // Push element into the items array

    this.items.push(val);

  }

  pop() {

    // Return top most element in the stack

    // and remove it from the stack

    if (!this.items.length) return "Underflow";

    return this.items.pop();

  }

  peek() {

    // return the top most element from the stack

    // but does'nt delete it.

    return this.items[this.items.length - 1];

  }

  getSize() {

    return this.items.length;

  }

  // print()

}