diff --git a/src/arrays.js b/src/arrays.js
index b995952..03e05e4 100644
--- a/src/arrays.js
+++ b/src/arrays.js
@@ -8,34 +8,86 @@ 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.
+  // elementseach(elements)
+  for (let i = 0; i < elements.length; i++) {
+    elements[i] = cb(elements[i]);
+  }
+  return elements;
 };
 
 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.
+  // each(elements, cb);
+  // while (!undefined) {
+  //   memo = cb(elements.shift());
+  // }
+  // return memo;
+  // for (let i = 0; i < elements.length; i++) {
+  //   memo += cb(elements[i]);
+  // }
+  // return memo;
+  // recursive
+  // if (elements.length === 0){
+  //   return memo;
+  // }
+  // return reduce(elements, cb, memo = elements.shift())
+  if (memo === undefined) {
+    memo = elements[0];
+  }
+  for (let i = 0; i < elements.length; i++) {
+    // elements[i] = cb(elements[i]);
+    memo = cb(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 arr = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i])) {
+      arr.push(elements[i]);
+    }
+  }
+  return arr;
 };
 
 /* 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 arr = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (typeof (elements[i]) === 'object') {
+      // pop array el, and iterate, and concate elements to original array
+      const arrayToBeBroken = elements.splice(i, 1)[0];
+      return flatten([...elements, ...arrayToBeBroken]);
+    }
+  }
+  return elements;
 };
 
 /* eslint-enable no-unused-vars, max-len */
diff --git a/src/class.js b/src/class.js
index 8276e29..7e00799 100644
--- a/src/class.js
+++ b/src/class.js
@@ -6,6 +6,16 @@
 // for a potential password that will be compared to the `password` property.
 // Return true if the potential password matches the `password` property.  Otherwise return false.
 
+class User {
+  constructor(options) {
+    this.email = options.email;
+    this.password = options.password;
+  }
+
+  comparePasswords(givenPassword) {
+    return givenPassword === this.password;
+  }
+}
 
 /* eslint-disable no-undef */ // Remove this comment once you write your classes.
 
@@ -19,6 +29,28 @@
 // `meow` that should return the string `<name> meowed!` where `<name>` is the `name`
 // property set on the Cat instance.
 
+class Animal {
+  constructor(options) {
+    this.age = options.age;
+  }
+
+  growOlder() {
+    return this.age;
+  }
+}
+
+class Cat extends Animal {
+  constructor(options) {
+    super();
+    this.name = options.name;
+  }
+
+  // super().growOlder();
+  meow() {
+    return `${this.name} meowed!`;
+  }
+}
+
 
 module.exports = {
   User,
diff --git a/src/closure.js b/src/closure.js
index 2d6592f..5ba23aa 100644
--- a/src/closure.js
+++ b/src/closure.js
@@ -3,6 +3,12 @@
 const counter = () => {
   // Return a function that when invoked increments and returns a counter variable.
   // Example: const newCounter = counter();
+  let count = 0;
+  const newCounter = () => {
+    count++;
+    return count;
+  };
+  return newCounter;
   // newCounter(); // 1
   // newCounter(); // 2
 };
@@ -11,11 +17,32 @@ 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.
+  let counter = 0;
+
+  const countObj = {
+    increment: () => {
+      counter++;
+      return counter;
+    }
+    decrement: () => {
+      counter = counter - 1;
+      return counter;
+    }
+  };
+
+  return countObj;
 };
 
 const limitFunctionCallCount = (cb, n) => {
   // Should return a function that invokes `cb`.
   // The returned function should only allow `cb` to be invoked `n` times.
+  let timesCalled = n;
+  const inner() => {
+    if (timesCalled <= timesCalled) {
+      return cb();
+    };
+  };
+  return inner;
 };
 
 /* Extra Credit */
diff --git a/src/es6.js b/src/es6.js
index eb846ab..583e161 100644
--- a/src/es6.js
+++ b/src/es6.js
@@ -7,50 +7,53 @@
 //----------------
 // const, =>, default parameters, arrow functions default return statements using ()
 
-var food = 'pineapple';
+const 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) {
-  this.username = options.username;
-  this.password = options.password;
-  this.sayHi = function() {
-    return this.username + ' says hello!';
-  };
-}
-
-var username = 'JavaScriptForever';
-var password = 'password';
-
-var me = new User({
-  username: username,
-  password: password,
+// const User = (options) {
+//   this.username = options.username;
+//   this.password = options.password;
+//   this.sayHi = () {
+//     // return this.username + ' says hello!';
+//     return `${this.username} says hello!`;
+//   };
+// }
+
+const username = 'JavaScriptForever';
+const password = 'password';
+
+const me = new User({
+  username,
+  // username: username,
+  password,
+  // password: password,
 });
 
 // ----------------
 // let, const, =>, ... (spread operator)
 
-var addArgs = function () {
-  var sum = 0;
-  for (var i = 0; i < arguments.length; i++) {
+const addArgs = () => {
+  let sum = 0;
+  for (let i = 0; i < arguments.length; i++) {
     sum += arguments[i];
   }
   return sum;
 };
 
-var argsToCb = function (cb) {
-  var args = Array.prototype.slice.call(arguments);
+const argsToCb = (cb) => {
+  const args = Array.prototype.slice.call(arguments);
   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
+console.log(result)
 /* eslint-enable */
diff --git a/src/objects.js b/src/objects.js
index ba39c6c..1187624 100644
--- a/src/objects.js
+++ b/src/objects.js
@@ -5,34 +5,61 @@ const 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
+  return Object.keys(obj);
 };
 
 const values = (obj) => {
   // Return all of the values of the object's own properties.
   // Ignore functions
   // http://underscorejs.org/#values
+  return Object.values(obj);
 };
 
 const mapObject = (obj, cb) => {
   // Like map for arrays, but for objects. Transform the value of each property in turn.
   // http://underscorejs.org/#mapObject
+  Object.keys(obj).forEach((currentKey) => {
+    obj[currentKey] = cb(obj[currentKey]);
+  });
+  return obj;
 };
 
 const pairs = (obj) => {
   // Convert an object into a list of [key, value] pairs.
   // http://underscorejs.org/#pairs
+  // return Object.enteries(obj);
+  const arr = [];
+  keys(obj).forEach((key) => {
+    arr.push([key, obj[key]]);
+  });
+  return arr;
 };
 
 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
+  // can keys be data types other than string?
+  const newObj = {};
+  Object.keys(obj).forEach((currentKey) => {
+    newObj[obj[currentKey]] = currentKey;
+  });
+  return newObj;
 };
 
 const defaults = (obj, defaultProps) => {
   // Fill in undefined properties that match properties on the `defaultProps` parameter object.
   // Return `obj`.
   // http://underscorejs.org/#defaults
+  const defaultPropKeys = keys(defaultProps);
+  const objectKeys = keys(obj);
+
+  defaultPropKeys.forEach((key) => {
+    if (!objectKeys.includes(key)) {
+      obj[key] = defaultProps[key];
+    }
+  });
+  return obj;
 };
 
 /* eslint-enable no-unused-vars */
diff --git a/src/recursion.js b/src/recursion.js
index eb65c57..018227a 100644
--- a/src/recursion.js
+++ b/src/recursion.js
@@ -3,14 +3,17 @@
 const nFibonacci = (n) => {
   // fibonacci sequence: 1 2 3 5 8 13 ...
   // return the nth number in the sequence
+  return n < 2 ? n : nFibonacci(n - 1) + nFibonacci(n - 2);
 };
 
 const nFactorial = (n) => {
   // factorial example: !5 = 5 * 4 * 3 * 2 * 1
   // return the factorial of `n`
+  return n < 2 ? n : n * nFactorial(n - 1);
 };
 
 /* Extra Credit */
+// how do you decrement or iterate recursively through obj?
 const checkMatchingLeaves = (obj) => {
   // return true if every property on `obj` is the same
   // otherwise return false
diff --git a/src/this.js b/src/this.js
index 8ea3020..3e1eeb2 100644
--- a/src/this.js
+++ b/src/this.js
@@ -5,10 +5,18 @@
 class User {
   constructor(options) {
     // set a username and password property on the user object that is created
+    this.password = options.password;
+    this.username = options.username;
   }
   // 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
   // return `true` if they match, otherwise return `false`
+  checkPassword(given) {
+    if (typeof given === 'string') {
+      return given === this.password;
+      // throw "given password isnt a string";
+    }
+  }
 }
 
 const me = new User({ username: 'LambdaSchool', password: 'correcthorsebatterystaple' });
@@ -19,13 +27,15 @@ const checkPassword = function comparePasswords(passwordToCompare) {
   // 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 `=>`
+  return this.password === passwordToCompare;
 };
 
 // invoke `checkPassword` on `me` by explicitly setting the `this` context
 // use .call, .apply, and .bind
+// checkPassword(me.this());
 
 // .call
-
+// checkPassword(me.password);
 // .apply
 
 // .bind
diff --git a/test.js b/test.js
new file mode 100644
index 0000000..3f6a6a7
--- /dev/null
+++ b/test.js
@@ -0,0 +1,156 @@
+// class User {
+//   constructor(options) {
+//     this.email = options.email;
+//     this.password = options.password;
+//   }
+
+//   comparePasswords(givenPassword) {
+//     return givenPassword === this.password;
+//   }
+// }
+
+// const nFibonacci = (n) => {
+//   // fibonacci sequence: 1 2 3 5 8 13 ...
+//   // return the nth number in the sequence
+//   return n < 2 ? n : nFibonacci(n - 1) + nFibonacci(n - 2)
+// };
+// const nFactorial = (n) => {
+//   // factorial example: !5 = 5 * 4 * 3 * 2 * 1
+//   // return the factorial of `n`
+//   return n < 2 ? n : n * nFactorial(n-1)
+// };
+// console.log(nFactorial(3));
+
+const counter = () => {
+  // Return a function that when invoked increments and returns a counter variable.
+  // Example: const newCounter = counter();
+  let count = 0;
+  const newCounter = () => {
+    count++;
+    return count;
+  };
+  return newCounter;
+  // const increment = () => count++;
+  // return increment();
+  // newCounter(); // 1
+  // newCounter(); // 2
+};
+
+newCounter = counter;
+console.log(newCounter);
+console.log(newCounter);
+
+// 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.
+//   let counter = 0;
+//   const increment = () => {
+//     counter++;
+//     return counter;
+//   }
+//   const decrement = () => {
+//     counter--;
+//     return counter;
+//   }
+// };
+
+// const c = counterFactory();
+
+
+
+// const newObj = {};
+// const obj = {"hello":5,"cake":"good"};
+
+// Object.keys(obj).forEach((currentKey) => {
+//     // console.log(currentKey, obj[currentKey]);
+//     newObj[obj[currentKey]] = currentKey;
+// });
+
+// const a = {
+//   x: 'hi',
+// };
+// const b = {
+//   banana: true,
+//   bubblegum: false,
+// };
+
+// const defaults = (obj, defaultProps) => {
+//   // Fill in undefined properties that match properties on the `defaultProps` parameter object.
+//   // Return `obj`.
+//   // http://underscorejs.org/#defaults
+//   // const defaultPropKeys = keys(defaultProps);
+//   // const objectKeys = keys(obj);
+
+//   // objectKeys.forEach((key) => {
+//   //   if (defaultPropKeys.includes(key)) {
+//   //     obj[key] = defaultProps[key];
+//   //   }
+//   // });
+//   // return obj;
+//   return Object.assign({}, obj, defaultProps);
+// };
+
+// console.log(defaults(a,b));
+// function reverseCase(str) {
+//   let newStr = '';
+//   str.split("").forEach((c) => {
+//     if (c === c.toUpperCase()) {
+//       newStr += c.toLowerCase();
+//     }
+//         if (c === c.toLowerCase()) {
+//       newStr += c.toUpperCase();
+//     }
+//   });
+//   return newStr;
+// }
+
+// function reverseCase(str) {
+//   return str.split("").forEach((c) => {
+//     if (c === c.toUpperCase()) {
+//       // newStr += c.toLowerCase();
+//       return c.toLowerCase();
+//     }
+//  if (c === c.toLowerCase()) {
+//       // newStr += c.toUpperCase();
+//       return c.toUpperCase();
+//     }
+//   }).join('');
+// }
+
+// function reverseCase(str) {
+//   return str.split("").map((c) => {
+//     if (c === c.toUpperCase()) {
+//       return c.toLowerCase();
+//     }
+//  if (c === c.toLowerCase()) {
+//       return c.toUpperCase();
+//     }
+//   }).join('');
+// }
+
+
+// console.log(reverseCase("HelloWorld"));
+// 'hELLO  wORLD' to be 'hELLO wORLD'
+
+// function evenOccurrence(arr) {
+//   const occurs = {};
+//   arr.forEach((num) => {
+//     if (Object.keys(occurs).includes(num.toString())) {
+//       occurs[num] = occurs[num] + 1;
+//     }
+//     else {
+//       occurs[num] = 1;
+//     }
+//   });
+
+//   Object.keys(occurs).forEach((key) => {
+//     if (occurs[key] % 2 === 0) {
+//       return parseInt(key);
+//     }
+//     return null;
+//   })
+// }
+
+// console.log(evenOccurrence([1, 7, 2, 4, 5, 6, 8, 9, 6, 4]))
+