diff --git a/package-lock.json b/package-lock.json
index c2d7130..baf523a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -3945,6 +3945,11 @@
       "dev": true,
       "optional": true
     },
+    "underscore": {
+      "version": "1.8.3",
+      "resolved": "https://registry.npmjs.org/underscore/-/underscore-1.8.3.tgz",
+      "integrity": "sha1-Tz+1OxBuYJf8+ctBCfKl6b36UCI="
+    },
     "user-home": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/user-home/-/user-home-2.0.0.tgz",
diff --git a/package.json b/package.json
index d23afbd..cecedb5 100644
--- a/package.json
+++ b/package.json
@@ -27,6 +27,7 @@
   },
   "dependencies": {
     "babel-preset-es2015": "^6.24.0",
-    "eslint-config-airbnb": "^14.1.0"
+    "eslint-config-airbnb": "^14.1.0",
+    "underscore": "^1.8.3"
   }
 }
diff --git a/src/arrays.js b/src/arrays.js
index b995952..41f65f4 100644
--- a/src/arrays.js
+++ b/src/arrays.js
@@ -8,34 +8,62 @@ const each = (elements, cb) => {
   // Iterates over a list of elements, yielding each in turn to the `cb` function.
   // This only needs to work with arrays.
   // based off http://underscorejs.org/#each
+  for (let i = 0; i < elements.length; i++) { cb(elements[i], i); }
 };
 
 const map = (elements, cb) => {
   // Produces a new array of values by mapping each value in list through a transformation function (iteratee).
   // Return the new array.
+  const newArr = [];
+  for (let i = 0; i < elements.length; i++) { newArr.push(cb(elements[i])); }
+  return newArr;
 };
 
 const reduce = (elements, cb, memo = elements.shift()) => {
   // Combine all elements into a single value going from left to right.
   // Elements will be passed one by one into `cb`.
-  // `memo` is the starting value.  If `memo` is undefined then make `elements[0]` the initial value.
+  // `memo` is the starting value.  If `memo` is undefined then make `elements[0]` the initial value
+  if (memo === undefined) memo = elements[0];
+  for (let i = 0; i < elements.length; ++i) {
+    memo = cb(memo, elements[i]);
+  }
+  return memo;
 };
 
+
 const find = (elements, cb) => {
   // Look through each value in `elements` and pass each element to `cb`.
   // If `cb` returns `true` then return that element.
   // Return `undefined` if no elements pass the truth test.
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i])) return elements[i];
+  }
+  return undefined;
 };
 
 const filter = (elements, cb) => {
   // Similar to `find` but you will return an array of all elements that passed the truth test
   // Return an empty array if no elements pass the truth test
+  const newArr = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i])) newArr.push(elements[i]);
+  }
+  return newArr;
 };
 
 /* Extra Credit */
 const flatten = (elements) => {
   // Flattens a nested array (the nesting can be to any depth).
   // Example: flatten([1, [2], [3, [[4]]]]); => [1, 2, 3, 4];
+  const newArr = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (elements[i].length) {
+      elements = elements.concat(elements[i]);
+    } else {
+      newArr.push(elements[i]);
+    }
+  }
+  return newArr;
 };
 
 /* eslint-enable no-unused-vars, max-len */
diff --git a/src/class.js b/src/class.js
index 8276e29..aaee2d7 100644
--- a/src/class.js
+++ b/src/class.js
@@ -19,6 +19,31 @@
 // `meow` that should return the string `<name> meowed!` where `<name>` is the `name`
 // property set on the Cat instance.
 
+class User {
+  constructor(options) {
+    this.email = options.email;
+    this.password = options.password;
+  }
+  comparePasswords(pass) {
+    if (pass === this.password) return true;
+    return false;
+  }
+}
+class Animal {
+  constructor(options) {
+    this.age = options.age;
+  }
+  growOlder() { return ++this.age; }
+
+}
+class Cat extends Animal {
+  constructor(options) {
+    super(options);
+    this.name = super.name;
+  }
+  meow() { return `${this.name} meowed!`; }
+}
+
 
 module.exports = {
   User,
diff --git a/src/closure.js b/src/closure.js
index 2d6592f..f57925c 100644
--- a/src/closure.js
+++ b/src/closure.js
@@ -5,17 +5,46 @@ const counter = () => {
   // Example: const newCounter = counter();
   // newCounter(); // 1
   // newCounter(); // 2
+  let count = 0;
+  const inc = () => {
+    count++;
+    return count;
+  };
+  return inc;
+};
+//
+const newObj = {
+  numUp: 0,
+  numDown: 0,
+  increment: function increment() {
+    this.numUp++;
+    return this.numUp;
+  },
+  decrement: function decrement() {
+    this.numDown--;
+    return this.numDown;
+  }
 };
-
 const counterFactory = () => {
   // Return an object that has two methods called `increment` and `decrement`.
   // `increment` should increment a counter variable in closure scope and return it.
   // `decrement` should decrement the counter variable and return it.
+  return newObj;
 };
 
+
 const limitFunctionCallCount = (cb, n) => {
   // Should return a function that invokes `cb`.
-  // The returned function should only allow `cb` to be invoked `n` times.
+  // The returned function should only allow `cb` to be invoked `n` times
+  let count = 0;
+  return (...args) => {
+    if (count < n) {
+      count++;
+    } else {
+      return null;
+    }
+    return cb(...args);
+  };
 };
 
 /* Extra Credit */
@@ -26,6 +55,11 @@ const cacheFunction = (cb) => {
   // If the returned function is invoked with arguments that it has already seen
   // then it should return the cached result and not invoke `cb` again.
   // `cb` should only ever be invoked once for a given set of arguments.
+  const cache = {};
+  return (arg) => {
+    if (arg in cache) return cache[arg];
+    return cache[arg] = cb(arg);
+  };
 };
 
 /* eslint-enable no-unused-vars */
diff --git a/src/es6.js b/src/es6.js
index eb846ab..baa93ff 100644
--- a/src/es6.js
+++ b/src/es6.js
@@ -7,30 +7,30 @@
 //----------------
 // const, =>, default parameters, arrow functions default return statements using ()
 
-var food = 'pineapple';
+let food = 'pineapple';
 
-var isMyFavoriteFood = function(food) {
+const isMyFavoriteFood = (food) => {
   food = food || 'thousand-year-old egg'; //This sets a default value if `food` is falsey
   return food === 'thousand-year-old egg';
 };
 
-var isThisMyFavorite = isMyFavoriteFood(food);
+const isThisMyFavorite = isMyFavoriteFood(food);
 
 //----------------
 //const, class, template literals, enhanced object literals (foo: foo, -> foo,)
 
-var User = function(options) {
+const User = (options) => {
   this.username = options.username;
   this.password = options.password;
-  this.sayHi = function() {
+  this.sayHi = () => {
     return this.username + ' says hello!';
   };
 }
 
-var username = 'JavaScriptForever';
-var password = 'password';
+const username = 'JavaScriptForever';
+const password = 'password';
 
-var me = new User({
+const me =  User({
   username: username,
   password: password,
 });
@@ -38,19 +38,19 @@ var me = new User({
 // ----------------
 // let, const, =>, ... (spread operator)
 
-var addArgs = function () {
-  var sum = 0;
-  for (var i = 0; i < arguments.length; i++) {
-    sum += arguments[i];
+const addArgs = (...arg) => {
+  let sum = 0;
+  for (let i = 0; i < arg.length; i++) {
+    sum += arg[i];
   }
   return sum;
 };
 
-var argsToCb = function (cb) {
-  var args = Array.prototype.slice.call(arguments);
+const argsToCb = (cb, ...arg) => {
+  const args = Array.prototype.slice.call(arg);
   return cb.apply(null, args.splice(1));
 };
 
-var result = argsToCb(addArgs, 1, 2, 3, 4, 5); //result should be 15
+const result = argsToCb(addArgs, 1, 2, 3, 4, 5); //result should be 15
 
 /* eslint-enable */
diff --git a/src/objects.js b/src/objects.js
index ba39c6c..2699b31 100644
--- a/src/objects.js
+++ b/src/objects.js
@@ -1,38 +1,57 @@
 // Complete the following underscore functions.
 // Reference http://underscorejs.org/ for examples.
 
-const keys = (obj) => {
+const keys = obj => Object.keys(obj);
   // Retrieve all the names of the object's properties.
   // Return the keys as strings in an array.
   // Based on http://underscorejs.org/#keys
-};
 
-const values = (obj) => {
+const values = obj => Object.values(obj);
   // Return all of the values of the object's own properties.
   // Ignore functions
   // http://underscorejs.org/#values
-};
 
 const mapObject = (obj, cb) => {
   // Like map for arrays, but for objects. Transform the value of each property in turn.
   // http://underscorejs.org/#mapObject
+  for (let i = 0; i < keys(obj).length; i++) {
+    obj[keys(obj)[i]] = cb(values(obj)[i]);
+  }
+  return obj;
 };
-
 const pairs = (obj) => {
   // Convert an object into a list of [key, value] pairs.
   // http://underscorejs.org/#pairs
+  const outArr = [];
+  for (let i = 0; i < keys(obj).length; i++) {
+    const subArr = [];
+    subArr.push(keys(obj)[i], values(obj)[i]);
+    outArr[i] = subArr;
+  }
+  return outArr;
 };
 
 const invert = (obj) => {
   // Returns a copy of the object where the keys have become the values and the values the keys.
   // Assume that all of the object's values will be unique and string serializable.
   // http://underscorejs.org/#invert
+  const newObj = {};
+  for (let i = 0; i < keys(obj).length; i++) {
+    newObj[values(obj)[i]] = keys(obj)[i];
+  }
+  return newObj;
 };
 
 const defaults = (obj, defaultProps) => {
   // Fill in undefined properties that match properties on the `defaultProps` parameter object.
   // Return `obj`.
   // http://underscorejs.org/#defaults
+  for (let i = 0; i < keys(defaultProps).length; i++) {
+    if (obj[keys(defaultProps)[i]] === undefined) {
+      obj[keys(defaultProps)[i]] = values(defaultProps)[i];
+    }
+  }
+  return obj;
 };
 
 /* eslint-enable no-unused-vars */
diff --git a/src/recursion.js b/src/recursion.js
index eb65c57..0c6627d 100644
--- a/src/recursion.js
+++ b/src/recursion.js
@@ -3,17 +3,29 @@
 const nFibonacci = (n) => {
   // fibonacci sequence: 1 2 3 5 8 13 ...
   // return the nth number in the sequence
+  if (n <= 1) return 1;
+  return nFibonacci(n - 1) + nFibonacci(n - 2);
 };
 
 const nFactorial = (n) => {
   // factorial example: !5 = 5 * 4 * 3 * 2 * 1
   // return the factorial of `n`
+  if (n === 0) return 1;
+  return n * nFactorial(n - 1);
 };
-
 /* Extra Credit */
 const checkMatchingLeaves = (obj) => {
   // return true if every property on `obj` is the same
   // otherwise return false
+  const checkBox = [];
+  function checkNested(subObj) {
+    for (let i = 0; i < Object.keys(subObj).length; i++) {
+      if (typeof subObj[Object.keys(subObj)[i]] !== 'object') checkBox.push(subObj[Object.keys(subObj)[i]]);
+      if (typeof subObj[Object.keys(subObj)[i]] === 'object') checkNested(subObj[Object.keys(subObj)[i]]);
+    }
+    return checkBox.every(allkeys => allkeys === checkBox[0]);
+  }
+  return checkNested(obj);
 };
 
 /* eslint-enable no-unused-vars */
diff --git a/src/this.js b/src/this.js
index 8ea3020..7991a96 100644
--- a/src/this.js
+++ b/src/this.js
@@ -5,6 +5,9 @@
 class User {
   constructor(options) {
     // set a username and password property on the user object that is created
+    this.username = options.username;
+    this.password = options.password;
+    this.checkPassword = string => string === this.password;
   }
   // create a method on the User class called `checkPassword`
   // this method should take in a string and compare it to the object's password property
@@ -14,18 +17,17 @@ class User {
 const me = new User({ username: 'LambdaSchool', password: 'correcthorsebatterystaple' });
 const result = me.checkPassword('correcthorsebatterystaple'); // should return `true`
 
-const checkPassword = function comparePasswords(passwordToCompare) {
+const checkPassword = passwordToCompare => this.password === passwordToCompare;
   // recreate the `checkPassword` method that you made on the `User` class
   // use `this` to access the object's `password` property.
   // do not modify this function's parameters
-  // note that we use the `function` keyword and not `=>`
-};
+  // note that we use the `function` keyword and not `=>'
 
 // invoke `checkPassword` on `me` by explicitly setting the `this` context
 // use .call, .apply, and .bind
-
 // .call
-
+console.log(checkPassword.call(this, User.password));
 // .apply
-
+console.log(checkPassword.apply(this, User.password));
 // .bind
+console.log(checkPassword.bind(this)());