diff --git a/arrays.js b/arrays.js
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+++ b/arrays.js
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+// Complete the following functions.
+// These functions only need to work with arrays.
+// Do NOT use the built in array methods to solve these. forEach, map, reduce, filter, includes, etc.
+// You CAN use concat, push, pop, etc. but do not use the exact method that you are replicating
+// You can use the functions that you have already written to help solve the other problems
+
+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.
+  // You should also pass the index into `cb` as the second argument
+  // 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 newArray = [];
+  for (let i = 0; i < elements.length; i++) {
+    newArray.push(cb(elements[i]));
+  }
+  return newArray;
+};
+
+const reduce = (elements, cb, startingValue) => {
+  // Combine all elements into a single value going from left to right.
+  // Elements will be passed one by one into `cb` along with the `startingValue`.
+  // `startingValue` should be the first argument passed to `cb` and the array element should be the second argument.
+  // `startingValue` is the starting value.  If `startingValue` is undefined then make `elements[0]` the initial value.
+  let memo = (startingValue === undefined) ? elements[0] : startingValue;
+  let i = (startingValue === undefined) ? 1 : 0;
+  for (; 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;
+};
+
+/* STRETCH PROBLEM */
+
+const flatten = (elements) => {
+  // Flattens a nested array (the nesting can be to any depth).
+  // Example: flatten([1, [2], [3, [[4]]]]); => [1, 2, 3, 4];
+};
+
+/* eslint-enable no-unused-vars, max-len */
+
+module.exports = {
+  each,
+  map,
+  reduce,
+  find,
+  filter,
+  flatten,
+};
diff --git a/callbacks.js b/callbacks.js
new file mode 100644
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--- /dev/null
+++ b/callbacks.js
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+/* eslint-disable */
+
+const firstItem = (arr, cb) => {
+  // firstItem passes the first item of the given array to the callback function.
+  cb(arr[0]);
+};
+
+const getLength = (arr, cb) => {
+  // getLength passes the length of the array into the callback.
+  cb(arr.length);
+};
+
+const last = (arr, cb) => {
+  // last passes the last item of the array into the callback.
+  const arrayLength = arr.length;
+  cb(arr[arrayLength - 1]);
+};
+
+const sumNums = (x, y, cb) => {
+  // sumNums adds two numbers (x, y) and passes the result to the callback.
+  const sum = x + y;
+  cb(sum);
+};
+
+const multiplyNums = (x, y, cb) => {
+  // multiplyNums multiplies two numbers and passes the result to the callback.
+  const sum = x * y;
+  cb(sum);
+};
+
+const contains = (item, list, cb) => {
+  // contains checks if an item is present inside of the given array/list.
+  // Pass true to the callback if it is, otherwise pass false.
+  for(let i = 0; i < list.length; i++){
+    if(item === list[i]) return cb(true); 
+  }
+  return cb(false);
+};
+
+/* STRETCH PROBLEM */
+
+const removeDuplicates = (array, cb) => {
+  // removeDuplicates removes all duplicate values from the given array.
+  // Pass the duplicate free array to the callback function.
+  // Do not mutate the original array.
+  const newArr = [];
+  for(let i = 0; i < array.length; i++){
+    contains(array[i], newArr, (isDuplicate) => {if(!isDuplicate) {
+      newArr.push(array[i]);
+      }
+    })
+  }
+  cb(newArr);
+};
+
+/* eslint-enable */
+module.exports = {
+  firstItem,
+  getLength,
+  last,
+  sumNums,
+  multiplyNums,
+  contains,
+  removeDuplicates,
+};
diff --git a/closure.js b/closure.js
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--- /dev/null
+++ b/closure.js
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+// Complete the following functions.
+
+const counter = () => {
+  // Return a function that when invoked increments and returns a counter variable.
+  // Example: const newCounter = counter();
+  // newCounter(); // 1
+  // newCounter(); // 2
+  let tracker = 0;
+  return () => { return ++tracker; };
+};
+
+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 tracker = 0;
+  return {
+    increment: () => {
+      return ++tracker;
+    },
+    decrement: () => {
+      return --tracker;
+    },
+  };
+};
+
+const limitFunctionCallCount = (cb, n) => {
+  // Should return a function that invokes `cb`.
+  // The returned function should only allow `cb` to be invoked `n` times.
+  let i = 0;
+  return (...args) => {
+    if (i < n) {
+      i++;
+      return cb(...args);
+    }
+    return null;
+  };
+};
+
+/* STRETCH PROBLEM */
+
+const cacheFunction = (cb) => {
+  // Should return a funciton that invokes `cb`.
+  // A cache (object) should be kept in closure scope.
+  // The cache should keep track of all arguments have been used to invoke this function.
+  // 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.
+};
+
+/* eslint-enable no-unused-vars */
+
+module.exports = {
+  counter,
+  counterFactory,
+  cacheFunction,
+  limitFunctionCallCount,
+};
diff --git a/objects.js b/objects.js
new file mode 100644
index 0000000..f4f9cae
--- /dev/null
+++ b/objects.js
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+// Complete the following underscore functions.
+// Reference http://underscorejs.org/ for examples.
+
+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
+  const keyArray = [];
+  Object.keys(obj).forEach((key) => {
+    keyArray.push(key);
+  });
+  return keyArray;
+};
+
+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
+  keys(obj).forEach((key) => {
+    obj[key] = cb(obj[key]);
+  });
+  return obj;
+};
+
+const pairs = (obj) => {
+  // Convert an object into a list of [key, value] pairs.
+  // http://underscorejs.org/#pairs
+  const list = [];
+  keys(obj).forEach((key) => {
+    const pair = [];
+    pair.push(key);
+    pair.push(obj[key]);
+    list.push(pair);
+  });
+  return list;
+};
+
+/* STRETCH PROBLEMS */
+
+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 invertedObject = {};
+  keys(obj).forEach((key) => {
+    const keyHolder = key;
+    const valueHolder = obj[key];
+    invertedObject[valueHolder] = keyHolder;
+  });
+  return invertedObject;
+};
+
+const defaults = (obj, defaultProps) => {
+  // Fill in undefined properties that match properties on the `defaultProps` parameter object.
+  // Return `obj`.
+  // http://underscorejs.org/#defaults
+  keys(defaultProps).forEach((key) => {
+    if (obj[key] === undefined) {
+      keys(defaultProps).forEach((defaultKey) => {
+        if (defaultKey === key) obj[key] = defaultProps[defaultKey];
+      });
+    }
+  });
+  return obj;
+};
+
+/* eslint-enable no-unused-vars */
+
+module.exports = {
+  keys,
+  values,
+  mapObject,
+  pairs,
+  invert,
+  defaults,
+};
diff --git a/script.js b/script.js
new file mode 100644
index 0000000..635625a
--- /dev/null
+++ b/script.js
@@ -0,0 +1 @@
+console.log("Hello world!");
\ No newline at end of file