JS Project I and II

src/arrays.js

@@ -14,12 +14,21 @@ 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 mappedElements = [];
+  for (let i = 0; i < elements.length; i++) {
+    mappedElements.push(cb(elements[i]));
+  }
+  return mappedElements;
 };
 
 const reduce = (elements, cb, startingValue) => {
@@ -28,26 +37,56 @@ 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.
+  let memo = startingValue;
+  let i = 0;
+  if (startingValue === undefined) {
+    memo = elements[0];
+    i++;
+  }
+  for (let i = 0; i < elements.length; i++) {
+    memo = cb(memo, elements[i]);
+  }
+  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];
+  }
 };
 
 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 filteredItems = [];
+  elements.forEach((item) => {
+    if (cb(item)) filteredItems.push(item);
+  });
+  return filteredItems;
 };
 
 /* 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];
+  const res = [];
+  const func = (arr) => {
+    for (let i = 0; i < arr.length; i++) {
+      if (Array.isArray(arr[i])) {
+        func(arr[i]);
+    } else {
+      res.push(arr[i]);
+    }
+  }
+ }
+ func(elements);
+ return res;
 };
 
 /* eslint-enable no-unused-vars, max-len */

src/callbacks.js

@@ -1,26 +1,46 @@
 const firstItem = (arr, cb) => {
   // firstItem passes the first item of the given array to the callback function.
+  const item = arr[0];
+  cb(item);
 };
 
 const getLength = (arr, cb) => {
   // getLength passes the length of the array into the callback.
+  const length = arr.length;
+  cb(length);
 };
 
 const last = (arr, cb) => {
   // last passes the last item of the array into the callback.
+  const lastItem = arr [arr.length - 1];
+  cb(lastItem);
 };
 
 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 prod = x * y;
+  cb(prod);
 };
 
 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.
+  test = false;
+
+  for (let i = 0; i <= arr.length; i++) {
+    if (item === arr[i]) {
+      test = true;
+      // return test;
+      // break;
+    }
+  }
+  cb(test);
 };
 
 /* STRETCH PROBLEM */
@@ -29,6 +49,19 @@ 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 res = [];
+  for (let i = 0; i <= newArr.length; i++) {
+    if(res.indexOf(array[i] !== -1) res.push(array[i]);
+    // for (let a = 1; a < newArr.length; a++) {
+    //   if (newArr[i] === newarr[a]) {
+    //     newArr.splice(a, 1);
+    //     console.log(newArr);
+    //     a = i+1;
+
+    //   }
+    // }
+  }
+  cb(res);
 };
 
 /* eslint-enable */

src/closure.js

@@ -5,17 +5,30 @@ const counter = () => {
   // Example: const newCounter = counter();
   // newCounter(); // 1
   // newCounter(); // 2
+  let count = 0;
+  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.
+  let count = 0;
+  return {
+    increment: () => ++count,
+    decrement: () => --count,
+  };
 };
 
 const limitFunctionCallCount = (cb, n) => {
   // 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();
+  };
 };
 
 /* STRETCH PROBLEM */

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.keys(obj).map(key => obj[key]);
 };
 
 const mapObject = (obj, cb) => {
   // Like map for arrays, but for objects. Transform the value of each property in turn.
   // http://underscorejs.org/#mapObject
+  const mappedObject = {};
+  Object.keys(obj).forEach((key) => {
+    obj[key] = cb(obj[key]);
+  });
+  return mappedObject;
 };
 
 const pairs = (obj) => {
   // Convert an object into a list of [key, value] pairs.
   // http://underscorejs.org/#pairs
+  return Object.keys(obj).map(key => [key, obj[key]]);
 };
 
 /* STRETCH PROBLEMS */
@@ -29,12 +37,24 @@ 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 = {};
+  Object.keys(obj).forEach((key) => {
+    const value = obj[key];
+    obj[value] = key;
+    delete obj[key];
+  });
+  return invertedObject;
 };
 
 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) => {
+    if (Object.prototype.hasOwnProperty.call(obj, key)) return;
+    obj[key] = defaultProps[key];
+  });
+  return obj;
 };
 
 /* eslint-enable no-unused-vars */