finished first item

examples.js

@@ -0,0 +1,6 @@
+name = 'Mark';
+console.log(name);
+
+for (let i = 0; i <= 10; i++) {
+    console.log(i);
+}

src/arrays.js

@@ -9,36 +9,68 @@ 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) => {
   // Produces a new array of values by mapping each value in list through a transformation function (iteratee).
   // Return the new array.
+  const x = [];
+  for (let i = 0; i < elements.length; i++) {
+    x.push(cb(elements[i]));
+  }
+  return x;
 };
 
 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 sum = elements[0];
+  if (startingValue !== undefined) sum = startingValue + elements[0];
+  for (let i = 1; i < elements.length; i++) {
+    sum = cb(sum, elements[i]);
+  }
+  return sum;
 };
 
 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 x = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i])) x.push(elements[i]);
+  }
+  return x;
 };
 
 /* 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];
+  let newArr = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (Array.isArray(elements[i])) {
+      newArr = newArr.concat(flatten(elements[i]));
+    } else {
+      newArr.push(elements[i]);
+    }
+  }
+  return newArr;
 };
 
 /* eslint-enable no-unused-vars, max-len */

src/callbacks.js

@@ -2,27 +2,34 @@
 
 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.
+  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.
+  let result = list.indexOf(item) >= 1 ? true : false;
+  cb(result);
 };
 
 /* STRETCH PROBLEM */
@@ -31,6 +38,8 @@ 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 removed = array.filter((item, index, inputArray) => inputArray.indexOf(item) === index);
+  cb(removed);
 };
 
 /* eslint-enable */

src/closure.js

@@ -5,28 +5,57 @@ const counter = () => {
   // Example: const newCounter = counter();
   // newCounter(); // 1
   // newCounter(); // 2
+  let count = 0;
+  return () => {
+    count++;
+    return count;
+  };
 };
 
 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 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 count = 0;
+  return {
+    increment: () => {
+      count++;
+      return count;
+    },
+    decrement: () => {
+      count--;
+      return count;
+    },
+  };
 };
 
 const limitFunctionCallCount = (cb, n) => {
-  // Should return a function that invokes `cb`.
-  // The returned function should only allow `cb` to be invoked `n` times.
+// Should return a function that invokes `cb`.
+// The returned function should only allow `cb` to be invoked `n` times.
+  let callCount = 0;
+  return (...args) => {
+    if (callCount === n) return null;
+    callCount++;
+    return cb(...args);
+  };
 };
 
 /* 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.
+// 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.
+  const cache = {};
+  return function (x) {
+    if (!(x in cache)) {
+      cache[x] = cb(x);
+    }
+    return cache[x];
+  };
 };
 
 /* eslint-enable no-unused-vars */

src/objects.js

@@ -5,36 +5,56 @@ 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
+    // Like map for arrays, but for objects. Transform the value of each property in turn.
+    // http://underscorejs.org/#mapObject
+  const mapped = {};
+
+  const myKeys = Object.keys(obj);
+  for (let i = 0; i < myKeys.length; i++) {
+    mapped[myKeys[i]] = cb(obj[myKeys[i]]);
+  }
+  return mapped;
 };
 
 const pairs = (obj) => {
   // Convert an object into a list of [key, value] pairs.
   // http://underscorejs.org/#pairs
+  return Object.keys(obj).map((key) => {
+    return [key, obj[key]];
+  });
 };
 
 /* 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 inverted = {};
+
+  const keyPair = Object.keys(obj);
+  for (let i = 0; i < keyPair.length; i++) {
+    inverted[obj[keyPair[i]]] = keyPair[i];
+  }
+
+  return inverted;
 };
 
 const defaults = (obj, defaultProps) => {
   // Fill in undefined properties that match properties on the `defaultProps` parameter object.
   // Return `obj`.
   // http://underscorejs.org/#defaults
+  Object.keys(defaultProps).forEach((key) => {
+    obj[key] = obj[key] || defaultProps[key];
+  });
+  return obj;
 };
 
 /* eslint-enable no-unused-vars */