JavaScript Data Structures: What Is A Stack + Example Code

By: Jeff Lewis

Github:

• Repository: data-structures-review
• File: stack.js

1. What Is A Stack?

A. Stack Definition:

A Stack is Linear Data Structure where data elements are arranged sequentially in an array.

Stacks and Queues are similar, but Stacks use the process of LIFO (Last In, First Out). To achieve this, the push and pop Javascript methods are used to create a Stack class in Javascript.

B. Time Complexity:

• Access: O(n)
• Search: O(n)
• Insert: O(1)
• Delete: O(1)

C. Space Complexity:

• O(n)

2. Stack Example Code

The code provided below shows 2 versions:

1. With Comments:

// Stack
class Stack {
  constructor () {
    this.storage = [];
  };
  // Add Element
  addElement(element) {
    this.storage.push(element);
  };
  // Remove Element
  removeElement() {
    // Check If Stack Is Not Empty
    if (!this.isEmpty()) {
      // Remove Last Element
      this.storage.pop();
    }
    else {
      console.log('Stack is empty');
    }
  };
  // View Last Element At Top Of The Stack
  viewLastElement() {
    // Check If Stack Is Not Empty
    if (!this.isEmpty()) {
      return this.storage[this.storage.length - 1];
    }
    else {
      console.log('Stack is empty');
    }
  };
  // Is Empty
  isEmpty() {
    // Check If Array Is Empty
    if (this.storage.length === 0) {
      return true;
    }
    else {
      return false;
    }
  };
  // View Stack
  viewStack() {
    return this.storage;
  };
};

2. Without Comments:

class Stack {
  constructor () {
    this.storage = [];
  };
  addElement(element) {
    this.storage.push(element);
  };
  removeElement() {
    if (!this.isEmpty()) {
      this.storage.pop();
    }
    else {
      console.log('Stack is empty');
    }
  };
  viewLastElement() {
    // Check If Stack Is Not Empty
    if (!this.isEmpty()) {
      return this.storage[this.storage.length - 1];
    }
    else {
      console.log('Stack is empty');
    }
  };
  isEmpty() {
    // Check If Array Is Empty
    if (this.storage.length === 0) {
      return true;
    }
    else {
      return false;
    }
  };
  viewStack() {
    return this.storage;
  };
};