From b5b5ebb85200c92df1eb770142594828d52522bf Mon Sep 17 00:00:00 2001
From: sunjieming <ben@lambdaschool.com>
Date: Wed, 12 Apr 2017 09:38:28 -0600
Subject: [PATCH] Add solutions

---
 src/arrays.js    | 27 +++++++++++++-
 src/closure.js   | 19 ++++++++++
 src/es6.js       | 97 ++++++++++++++++++++++++++++++++----------------
 src/objects.js   | 26 +++++++++++--
 src/recursion.js | 22 +++++++++++
 src/this.js      | 10 +++++
 6 files changed, 165 insertions(+), 36 deletions(-)

diff --git a/src/arrays.js b/src/arrays.js
index 8402703..da8e7d2 100644
--- a/src/arrays.js
+++ b/src/arrays.js
@@ -4,34 +4,59 @@
 /* eslint-disable no-unused-vars, max-len */
 
 const each = (elements, cb) => {
+  for (let i = 0; i < elements.length; i++) {
+    cb(elements[i], i);
+  }
   // 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
 };
 
 const map = (elements, cb) => {
+  const mappedArr = [];
+  each(elements, item => (mappedArr.push(cb(item))));
+  return mappedArr;
   // Produces a new array of values by mapping each value in list through a transformation function (iteratee).
   // Return the new array.
+  // return elements.map(cb);
 };
 
-const reduce = (elements, cb, memo) => {
+const reduce = (elements, cb, memo = elements.shift()) => {
+  each(elements, (item) => {
+    memo = cb(memo, item);
+  });
+  return memo;
   // 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.
 };
 
 const find = (elements, cb) => {
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i])) return elements[i];
+  }
+  return undefined;
   // 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.
 };
 
 const filter = (elements, cb) => {
+  const filteredValues = [];
+  each(elements, (item) => {
+    if (cb(item)) filteredValues.push(item);
+  });
+  return filteredValues;
   // 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 flatten = (elements) => {
+  const flattenedArr = reduce(elements, (memo, item) => {
+    if (Array.isArray(item)) return memo.concat(flatten(item));
+    return memo.concat(item);
+  }, []);
+  return flattenedArr;
   // Flattens a nested array (the nesting can be to any depth).
   // Example: flatten([1, [2], [3, [[4]]]]); => [1, 2, 3, 4];
 };
diff --git a/src/closure.js b/src/closure.js
index 0284314..a6d4667 100644
--- a/src/closure.js
+++ b/src/closure.js
@@ -3,6 +3,8 @@
 /* eslint-disable no-unused-vars */
 
 const counter = () => {
+  let count = 0;
+  return () => (++count);
   // Return a function that when invoked increments and returns a counter variable.
   // Example: const newCounter = counter();
   // newCounter(); // 1
@@ -10,17 +12,34 @@ const counter = () => {
 };
 
 const counterFactory = () => {
+  let count = 0;
+  return {
+    increment: () => (++count),
+    decrement: () => (--count),
+  };
   // 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.
 };
 
 const limitFunctionCallCount = (cb, n) => {
+  let callCount = 0;
+  return (...args) => {
+    if (callCount === n) return null;
+    callCount++;
+    return cb(...args);
+  };
   // Should return a function that invokes `cb`.
   // The returned function should only allow `cb` to be invoked `n` times.
 };
 
 const cacheFunction = (cb) => {
+  const cache = {};
+  return (input) => {
+    if (Object.prototype.hasOwnProperty.call(cache, input)) return cache[input];
+    cache[input] = cb(input);
+    return cache[input];
+  };
   // 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.
diff --git a/src/es6.js b/src/es6.js
index eb846ab..8866372 100644
--- a/src/es6.js
+++ b/src/es6.js
@@ -7,50 +7,85 @@
 //----------------
 // const, =>, default parameters, arrow functions default return statements using ()
 
-var food = 'pineapple';
+// var food = 'pineapple';
+//
+// var isMyFavoriteFood = function(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);
 
-var isMyFavoriteFood = function(food) {
-  food = food || 'thousand-year-old egg'; //This sets a default value if `food` is falsey
-  return food === 'thousand-year-old egg';
-};
+// ----------------
+
+const food = 'pineapple';
+
+const isMyFavoriteFood = (food = 'thousand-year-old egg') => (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!';
-  };
+//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,
+// });
+
+// ----------------
+
+class User {
+  constructor(options) {
+    this.username = options.username;
+    this.password = options.password;
+  }
+  sayHi() {
+    return `${this.username} says hello!`;
+  }
 }
 
-var username = 'JavaScriptForever';
-var password = 'password';
+const username = 'JavaScriptForever';
+const pasword = 'password';
 
-var me = new User({
-  username: username,
-  password: password,
+const me = new User({
+  username,
+  password,
 });
 
 // ----------------
 // let, const, =>, ... (spread operator)
 
-var addArgs = function () {
-  var sum = 0;
-  for (var i = 0; i < arguments.length; i++) {
-    sum += arguments[i];
-  }
-  return sum;
-};
+// var addArgs = function () {
+//   var sum = 0;
+//   for (var i = 0; i < arguments.length; i++) {
+//     sum += arguments[i];
+//   }
+//   return sum;
+// };
+//
+// var argsToCb = function (cb) {
+//   var 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
+
+// ----------------
 
-var argsToCb = function (cb) {
-  var args = Array.prototype.slice.call(arguments);
-  return cb.apply(null, args.splice(1));
-};
+const addArgs = (...args) => (args.reduce((memo, val) => (memo + val)));
 
-var result = argsToCb(addArgs, 1, 2, 3, 4, 5); //result should be 15
+const argsToCb = (cb, ...args) => (cb(...args));
 
+const result = argsToCb(addArgs, 1, 2, 3, 4, 5);
 /* eslint-enable */
diff --git a/src/objects.js b/src/objects.js
index 43e5376..9bb9c2f 100644
--- a/src/objects.js
+++ b/src/objects.js
@@ -1,37 +1,55 @@
 // Complete the following underscore functions.
 // Reference http://underscorejs.org/ for examples.
 
-/* eslint-disable no-unused-vars */
+/* eslint-disable no-unused-vars, arrow-body-style */
 
 const keys = (obj) => {
+  return Object.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 values = (obj) => {
+  return Object.keys(obj).map((key) => {
+    return obj[key];
+  });
+};
   // Return all of the values of the object's own properties.
   // Ignore functions
   // http://underscorejs.org/#values
-};
+
 
 const mapObject = (obj, cb) => {
+  Object.keys(obj).forEach(key => (obj[key] = cb(obj[key])));
+  return obj;
   // Like map for arrays, but for objects. Transform the value of each property in turn.
   // http://underscorejs.org/#mapObject
 };
 
-const pairs = (obj) => {
+const pairs = obj => (Object.keys(obj).map(key => ([key, obj[key]])));
   // Convert an object into a list of [key, value] pairs.
   // http://underscorejs.org/#pairs
-};
+
 
 const invert = (obj) => {
+  Object.keys(obj).forEach((key) => {
+    const newKey = obj[key];
+    obj[newKey] = key;
+    delete obj[key];
+  });
+  return 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 defaults = (obj, defaultProps) => {
+  Object.keys(defaultProps).forEach((key) => {
+    if (Object.prototype.hasOwnProperty.call(obj, key)) return;
+    obj[key] = defaultProps[key];
+  });
+  return obj;
   // Fill in undefined properties that match properties on the `defaultProps` parameter object.
   // Return `obj`.
   // http://underscorejs.org/#defaults
diff --git a/src/recursion.js b/src/recursion.js
index f773ee1..be97a71 100644
--- a/src/recursion.js
+++ b/src/recursion.js
@@ -3,16 +3,38 @@
 /* eslint-disable no-unused-vars */
 
 const nFibonacci = (n) => {
+  if (n <= 1) return 1;
+  return nFibonacci(n - 1) + nFibonacci(n - 2);
   // fibonacci sequence: 1 2 3 5 8 13 ...
   // return the nth number in the sequence
 };
 
 const nFactorial = (n) => {
+  if (n < 1) return 1;
+  return n * nFactorial(n - 1);
   // factorial example: !5 = 5 * 4 * 3 * 2 * 1
   // return the factorial of `n`
 };
 
 const checkMatchingLeaves = (obj) => {
+  let val;
+  let allMatch = true;
+  const checkLeaves = (object) => {
+    Object.keys(object).forEach((key) => {
+      if (val === undefined && typeof key !== 'object') {
+        val = object[key];
+        return undefined;
+      }
+      if (typeof object[key] === 'object') return checkLeaves(object[key]);
+      if (object[key] !== val) {
+        allMatch = false;
+        return undefined;
+      }
+      return undefined;
+    });
+  };
+  checkLeaves(obj);
+  return allMatch;
   // return true if every property on `obj` is the same
   // otherwise return false
 };
diff --git a/src/this.js b/src/this.js
index b88e142..cc340a4 100644
--- a/src/this.js
+++ b/src/this.js
@@ -6,8 +6,13 @@
 
 class User {
   constructor(options) {
+    this.username = options.username;
+    this.password = options.password;
     // set a username and password property on the user object that is created
   }
+  checkPassword(passwordToCompare) {
+    return this.password === passwordToCompare;
+  }
   // 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`
@@ -19,6 +24,7 @@ const me = new User({ username: 'LambdaSchool', password: 'correcthorsebatteryst
 const result = me.checkPassword('correcthorsebatterystaple'); // should return `true`
 
 const checkPassword = function comparePasswords(passwordToCompare) {
+  return this.password === passwordToCompare;
   // recreate the `checkPassword` method that you made on the `User` class
   // use `this` to access the object's `password` property.
   // do not modify this function's parameters
@@ -30,7 +36,11 @@ const checkPassword = function comparePasswords(passwordToCompare) {
 // use .call, .apply, and .bind
 
 // .call
+checkPassword.call(me, 'correcthorsebatterystaple');
 
 // .apply
+checkPassword.apply(me, 'correcthorsebatterystaple');
 
 // .bind
+const boundPasswordCheck = checkPassword.bind(me);
+boundPasswordCheck('correcthorsebatterystaple');