BigCoffee.js

var BigCoffee = function(selector) {
  var elements = document.querySelectorAll(selector),
      index = 0;

  if (this === window) {
    return new BigCoffee(selector);
  }

  for (; index < elements.length; index++) {
    this[index] = elements[index];
  }

  this.length = elements.length;
  return this;
};

BigCoffee.prototype = {
  map: function(callback) {
    var results = [],
        index = 0;

    for (; index < this.length; index++) {
      results.push(callback.call(this, this[index], index));
    }

    return results;
  },

  forEach: function(callback) {
    this.map(callback);
    return this;
  },

  // CLASSES
  addClass: function(className) {
    return this.forEach(function(element) {
      element.classList.add(className);
    });
  },

  hasClass: function() {
    return 105;
  },

  removeClass: function(className) {
    return this.forEach(function(element) {
      element.classList.remove(className);
    });
  },

  // ATTRIBUTES
  getAttribute: function(attribute) {
    return this.forEach(function(element) {
      element.getAttribute(attribute);
    });
  },

  removeAttribute: function(attribute) {
    return this.forEach(function(element) {
      element.removeAttribute(attribute);
    });
  },

  setAttribute: function(attribute, value) {
    return this.forEach(function(element) {
      element.setAttribute(attribute, value);
    });
  }
};