Mathias Bakken

package.json

@@ -27,6 +27,7 @@
     "regenerator-runtime": "^0.10.3"
   },
   "dependencies": {
-    "eslint-config-airbnb": "^14.1.0"
+    "eslint-config-airbnb": "^14.1.0",
+    "yarn": "^1.5.1"
   }
 }

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 myArr = [];
+  for (let i = 0; i < elements.length; i++) {
+    myArr.push(cb(elements[i], i));
+  }
+  return myArr;
 };
 
 const reduce = (elements, cb, startingValue) => {
@@ -28,26 +36,48 @@ 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.
+  const elementsCopy = elements.slice();
+  let memo = startingValue || elementsCopy.shift();
+  each(elementsCopy, (item) => {
+    memo = cb(memo, item);
+  });
+  return memo;
 };
 
 const find = (elements, cb) => {
   // Do NOT use .includes, to complete this function.
   // 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) => {
   // 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 newArray = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i])) {
+      newArray.push(elements[i]);
+    }
+  }
+  return newArray;
 };
 
 /* 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];
+  return elements.reduce((memo, num) => {
+    return memo.concat(Array.isArray(num) ? flatten(num) : num);
+  }, []);
 };
 
 /* eslint-enable no-unused-vars, max-len */

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.
+  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 */
@@ -29,8 +35,14 @@ 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 arr = [];
+  for (let i = 0; i < array.length; i++) {
+    if (!arr.includes(array[i])) {
+      arr.push(array[i]);
+    }
+  }
+  cb(arr);
 };
-
 /* eslint-enable */
 module.exports = {
   firstItem,

src/closure.js

@@ -1,32 +1,59 @@
 // 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
+// Return a function that when invoked increments and returns a counter variable.
+// Example: const newCounter = counter();
+// newCounter(); // 1
+// newCounter(); // 2
+  let count = 0;
+  const counting = () => {
+    count++;
+    return count;
+  };
+  return counting;
 };
 
 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 count1 = 0;
+  let count2 = 0;
+  const newObj = {
+    increment: () => {
+      count1++;
+      return count1;
+    },
+    decrement: () => {
+      count2--;
+      return count2;
+    }
+  };
+  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.
+// Should return a function that invokes `cb`.
+// The returned function should only allow `cb` to be invoked `n` times.
+  let timesInvoked = 0;
+  return (...args) => {
+    if (timesInvoked === n) {
+      return null;
+    }
+    timesInvoked++;
+    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.
 };
 
 /* eslint-enable no-unused-vars */

src/objects.js

@@ -5,22 +5,43 @@ 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 objVal = {};
+  const objEntry = Object.entries(obj);  // [[a: 1], [b: 2], [c: 3]]
+  for (let i = 0; i < objEntry.length; i++) {
+    objEntry[i][1] = cb(objEntry[i][1]);
+    // newObj.objEntry[i] = objEntry[i][1];
+  }
+  // magic to turn our nested arrays into objects
+  objEntry.forEach((a) => {
+    let p = objVal;
+    const v = a.pop();
+    const k = a.reduce((r, b) => {
+      p[r] = p[r] || {};
+      p = p[r];
+      return b;
+    });
+    p[k] = v;
+  });
+  return objVal;
 };
 
 const pairs = (obj) => {
   // Convert an object into a list of [key, value] pairs.
   // http://underscorejs.org/#pairs
+  return Object.entries(obj);
 };
 
 /* STRETCH PROBLEMS */