--description--

In the last section, we talked about what a stack is and how we can use an array to represent a stack. In this section, we will be creating our own stack class. Although you can use arrays to create stacks, sometimes it is best to limit the amount of control we have with our stacks. Apart from the push and pop method, stacks have other useful methods. Let's add a peek, isEmpty, and clear method to our stack class.

--instructions--

Write a push method that pushes an element to the top of the stack, a pop method that removes and returns the element on the top of the stack, a peek method that looks at the top element in the stack, an isEmpty method that checks if the stack is empty, and a clear method that removes all elements from the stack. Normally stacks don't have this, but we've added a print helper method that console logs the collection.

--hints--

Your Stack class should have a push method.

assert(
  (function () {
    var test = new Stack();
    return typeof test.push === 'function';
  })()
);

Your Stack class should have a pop method.

assert(
  (function () {
    var test = new Stack();
    return typeof test.pop === 'function';
  })()
);

Your Stack class should have a peek method.

assert(
  (function () {
    var test = new Stack();
    return typeof test.peek === 'function';
  })()
);

Your Stack class should have a isEmpty method.

assert(
  (function () {
    var test = new Stack();
    return typeof test.isEmpty === 'function';
  })()
);

Your Stack class should have a clear method.

assert(
  (function () {
    var test = new Stack();
    return typeof test.clear === 'function';
  })()
);

The peek method should return the top element of the stack

assert(
  (function () {
    var test = new Stack();
    test.push('CS61');
    test.push('CS50');
    return test.peek() === 'CS50' && test.peek() === 'CS50';
  })()
);

The pop method should remove and return the top element of the stack

assert(
  (function () {
    var test = new Stack();
    test.push('CS61');
    test.push('CS50');
    return test.pop() === 'CS50' && test.pop() === 'CS61';
  })()
);

The isEmpty method should return true if a stack does not contain any elements

assert(
  (function () {
    var test = new Stack();
    return test.isEmpty();
  })()
);

The clear method should remove all element from the stack

assert(
  (function () {
    var test = new Stack();
    test.push('CS61');
    test.push('CS50');
    test.clear();
    return test.isEmpty();
  })()
);

--seed--

--seed-contents--

function Stack() {
  var collection = [];
  this.print = function() {
    console.log(collection);
  };
  // Only change code below this line

  // Only change code above this line
}

--solutions--

class Stack {
  constructor() {
    this.collection = [];
  }
  print() {
    console.log(this.collection);
  }
  push(val) {
    this.collection.push(val);
  }
  pop() {
    return this.collection.pop();
  }
  peek() {
    return this.collection[this.collection.length - 1];
  }
  isEmpty() {
    return this.collection.length === 0;
  }
  clear() {
    return (this.collection.length = 0);
  }
}