22. DOM Manipulation Library - Chaining

HTML

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<p>
  <button class="btn-blue button" id="button-1">Button 1</button>
  <button class="btn-blue button here-is-johnny" id="button-2">Button 2</button>
  <button class="btn-blue button" id="button-3">Button 3</button>
  <button class="btn-blue button" id="button-4">Button 4</button>
  <button class="btn-blue button" id="button-5">Button 5</button>
  <button class="btn-blue button here-is-johnny" id="button-6">Button 6</button>
</p>

JavaScript

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/* Modify any methods that you can to support chaining. 
Ideally, the methods to add and remove classes should be chainable.*/

const $ = (function () {

  // Create Constructor function here
  const Constructor = function (selector) {
    this.elements = document.querySelectorAll(selector);
  };

  // Immutable copy of the matching elements
  Constructor.prototype.items = function () {
    return Array.prototype.slice.call(this.elements);
  };

  // Get first item
  Constructor.prototype.first = function () {
    return this.elements[0];
  }

  // Get last item
  Constructor.prototype.last = function () {
    return this.elements[this.elements.length - 1];
  }

  // Add class to element
  Constructor.prototype.addClass = function (newClass) {
    this.items().forEach(element => {
      element.classList.add(newClass);
    })
    return this;
  };

  // Remove class from element
  Constructor.prototype.removeClass = function (newClass) {
    this.items().forEach(element => {
      element.classList.remove(newClass);
    })
    return this;
  };

  return Constructor;
})();

// Create new instance
const btns = new $('.button')

// Check the console logs in dev tools
console.log('$.items()', btns.items());
console.log('$.first()', btns.first());
console.log('$.last()', btns.last());

// Add and remove class
btns.addClass('btn-purple').removeClass('btn-blue');