Introduction to Stacks and Queues in JavaScript

Introduction: Stacks and Queues

Welcome to an exciting exploration of two fundamental data structures: Stacks and Queues! Remember, data structures store and organize data in a manner that is structured and efficient. Stacks and Queues are akin to stacking plates and standing in a line, respectively. Intriguing, isn't it? Let's dive in!

Stacks: Last In, First Out (LIFO)

A Stack adheres to the "Last In, First Out" or LIFO principle. It's like a pile of plates where the last plate added is the first one to be removed. JavaScript uses arrays to create a stack, with push() used for insert (push), and pop() used for remove (pop, return the element that has been removed). Let's explore this using a pile of plates. JavaScript class StackOfPlates {constructor() {this.stack = [];} // Inserts a plate at the top of the stack addPlate(plate) {this.stack.push(plate);} // Removes the top plate from the stack removePlate() {if (this.stack.length === 0) {return "No plates left to remove!";} return this.stack.pop();}} // Create a stack of plates const plates = new StackOfPlates(); plates.addPlate('Plate'); // Pushing a plate plates.addPlate('Another Plate'); // Pushing another plate // Let's remove a plate; it should be the last one we added. console.log('Removed:', plates.removePlate()); // Outputs: Removed: Another Plate The last plate added was removed first, demonstrating the LIFO property of a stack.

Queues: First In, First Out (FIFO)

A Queue represents the "First In, First Out" or FIFO principle, much like waiting in line at the grocery store. In JavaScript, we can use arrays to achieve this behavior, using push() for enqueue (insert at the end) and shift() for dequeue (remove from the front, return the element that has been removed). Let's examine this through a queue of people. JavaScript class QueueOfPeople {constructor() {this.queue = [];} // Add a person to the end of the queue enqueuePerson(person) {this.queue.push(person);} // Remove the first person from the queue (who has been waiting the longest) dequeuePerson() {if (this.queue.length === 0) {return "No people left to dequeue!";} return this.queue.shift();}} // Create a queue of people const people = new QueueOfPeople(); people.enqueuePerson('Person 1'); // Person 1 enters the queue people.enqueuePerson('Person 2'); // Person 2 arrives after Person 1 // Who's next in line? It must be Person 1! console.log('Removed:', people.dequeuePerson()); // Outputs: Removed: Person 1 Here, Person 1, the first to join the queue, left before Person 2, demonstrating the FIFO property of a queue.

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Mastering Stack and Queue Operations With a Class

Let's depict the two structures in a text editor that features an Undo mechanism (a Stack) and a Print Queue.

JavaScript

class TextEditor {
  constructor() {
    this.stack = [];
    this.queue = [];
  }

  // Make a change (e.g., edit text, insert image, change font)
  makeChange(action) {
    this.stack.push(action); // Add to the stack of actions
  }

  // Undo the most recent change
  undoChange() {
    if (this.stack.length === 0) {
      return "No changes to undo!";
    }
    return this.stack.pop(); // Remove the last action from the stack
  }

  // Add a document to the queue for printing
  addToPrint(doc) {
    this.queue.push(doc);
  }

  // Print the document that has been waiting the longest
  printDoc() {
    if (this.queue.length === 0) {
      return "No documents in print queue!";
    }
    return this.queue.shift(); // Remove the first document from the queue
  }
}

// Use our text editor!
const editor = new TextEditor();
editor.makeChange("Changed font size"); // Make a change
editor.makeChange("Inserted image"); // Make another change
// Let's undo a change. It should be the last change we made.
console.log('Undo:', editor.undoChange());  // Undo: Inserted image

editor.addToPrint("Proposal.docx"); // Queue a document for printing
editor.addToPrint("Report.xlsx"); // Queue another document
// Let's print a document. It should be the document that has been waiting the longest.
console.log('Print:', editor.printDoc());  // Print: Proposal.docx

class TextEditor {
  constructor() {
    this.stack = [];
    this.queue = [];
  }

  // Make a change (e.g., edit text, insert image, change font)
  makeChange(action) {
    this.stack.push(action); // Add to the stack of actions
  }

  // Undo the most recent change
  undoChange() {
    if (this.stack.length === 0) {
      return "No changes to undo!";
    }
    return this.stack.pop(); // Remove the last action from the stack
  }

  // Add a document to the queue for printing
  addToPrint(doc) {
    this.queue.push(doc);
  }

  // Print the document that has been waiting the longest
  printDoc() {
    if (this.queue.length === 0) {
      return "No documents in print queue!";
    }
    return this.queue.shift(); // Remove the first document from the queue
  }
}

// Use our text editor!
const editor = new TextEditor();
editor.makeChange("Changed font size"); // Make a change
editor.makeChange("Inserted image"); // Make another change
// Let's undo a change. It should be the last change we made.
console.log('Undo:', editor.undoChange());  // Undo: Inserted image

editor.addToPrint("Proposal.docx"); // Queue a document for printing
editor.addToPrint("Report.xlsx"); // Queue another document
// Let's print a document. It should be the document that has been waiting the longest.
console.log('Print:', editor.printDoc());  // Print: Proposal.docx

This code reintroduces the concepts of a Stack (Undo feature) and Queue (Print queue) in the context of a real-life scenario.

Introduction: Stacks and Queues

Stacks: Last In, First Out (LIFO)

Queues: First In, First Out (FIFO)

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Stacks and Queues: When and Where to Use?

Mastering Stack and Queue Operations With a Class

Lesson Summary