diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 00000000..73b7a5cd
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,14 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Launch Program",
+            "program": "${workspaceFolder}/index.js"
+        }
+    ]
+}
\ No newline at end of file
diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 00000000..3b664107
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,3 @@
+{
+    "git.ignoreLimitWarning": true
+}
\ No newline at end of file
diff --git a/src/arrays.js b/src/arrays.js
index 968a168b..28b82246 100644
--- a/src/arrays.js
+++ b/src/arrays.js
@@ -14,12 +14,20 @@ const each = (elements, cb) => {
   // 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) => {
   // Do NOT use .map, to complete this function.
   // 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, startingValue) => {
@@ -28,6 +36,13 @@ const reduce = (elements, cb, startingValue) => {
   // 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.
+  if (startingValue === undefined) {
+    startingValue = elements.shift();
+  }
+  for (let i = 0; i < elements.length; i++) {
+    startingValue = cb(startingValue, elements[i]);
+  }
+  return startingValue;
 };
 
 const find = (elements, cb) => {
@@ -35,12 +50,24 @@ 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];
+    }
+  }
 };
 
 const filter = (elements, cb) => {
   // Do NOT use .filter, to complete this function.
   // 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 output = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i])) {
+      output.push(elements[i]);
+    }
+  }
+  return output;
 };
 
 /* STRETCH PROBLEM */
@@ -48,6 +75,15 @@ const filter = (elements, cb) => {
 const flatten = (elements) => {
   // Flattens a nested array (the nesting can be to any depth).
   // Example: flatten([1, [2], [3, [[4]]]]); => [1, 2, 3, 4];
+  let output = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (Array.isArray(elements[i])) {
+      output = output.concat(flatten(elements[i]));
+    } else {
+      output.push(elements[i]);
+    }
+  }
+  return output;
 };
 
 /* eslint-enable no-unused-vars, max-len */
diff --git a/src/callbacks.js b/src/callbacks.js
index 53917475..108b60f4 100644
--- a/src/callbacks.js
+++ b/src/callbacks.js
@@ -1,26 +1,32 @@
 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.
+  cb(arr[arr.length - 1]);
 };
 
 const sumNums = (x, y, cb) => {
-  // sumNums adds two numbers (x, y) and passes the result to the callback.
+  //   // sumNums adds two numbers (x, y) and passes the result to the callback.
+  cb(x + y);
 };
 
 const multiplyNums = (x, y, cb) => {
   // multiplyNums multiplies two numbers and passes the result to the callback.
+  cb(x * y);
 };
 
 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.
+  cb(list.includes(item));
 };
 
 /* STRETCH PROBLEM */
@@ -29,6 +35,13 @@ 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 output = [];
+  for (let i = 0; i < array.length; i++) {
+    if (!output.includes(array[i])) {
+      output.push(array[i]);
+    }
+  }
+  cb(output);
 };
 
 /* eslint-enable */
diff --git a/src/objects.js b/src/objects.js
index 2898d4d4..2856f5bd 100644
--- a/src/objects.js
+++ b/src/objects.js
@@ -5,22 +5,30 @@ 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
+  const arrKey = keys(obj);
+  for (let i = 0; i < arrKey.length; i++) {
+    obj[arrKey[i]] = cb(obj[arrKey[i]]);
+  }
+  return obj;
 };
 
 const pairs = (obj) => {
   // Convert an object into a list of [key, value] pairs.
   // http://underscorejs.org/#pairs
+  return Object.entries(obj);
 };
 
 /* STRETCH PROBLEMS */
@@ -29,12 +37,25 @@ 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 keysArr = keys(obj); //Object.keys(obj)
+  const dupe = {};
+  for (let i = 0; i < keysArr.length; i++) {
+    dupe[obj[keysArr[i]]] = keysArr[i];
+  }
+  return dupe;
 };
 
 const defaults = (obj, defaultProps) => {
   // Fill in undefined properties that match properties on the `defaultProps` parameter object.
   // Return `obj`.
   // http://underscorejs.org/#defaults
+  const keysArr = keys(defaultProps);
+  for (let i = 0; i < keysArr.length; i++) {
+    if (obj[keysArr[i]] === undefined) {
+      obj[keysArr[i]] = defaultProps[keysArr[i]];
+    }
+  }
+  return obj;
 };
 
 /* eslint-enable no-unused-vars */