Ilho Kim - Javascript-I

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) => {
@@ -28,26 +36,63 @@ 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);
+  });
 };
 
 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.
+  let test = false;
+  let index = 0;
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i]) === true) {
+      test = true;
+      index = i;
+    }
+  }
+
+  if (test === true) {
+    return elements[index];
+  }
+  return 'undifined';
 };
 
 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 newArr = [];
+  for (let i = 0; i < elements.length; i++) {
+    if (cb(elements[i]) === true) {
+      newArr.push(elements[i]);
+    }
+    return newArr;
+  }
 };
 
 /* 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

@@ -1,34 +1,51 @@
 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.
+  // 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.
+  let test = false;
+  for (let i = 0; i <= list.length; i++) {
+    if (item === list[i]) {
+      test = true;
+    }
+  }
+  cb(test);
 };
 
 /* STRETCH PROBLEM */
 
 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.
+  // Do not mutate the original array
 };
 
 /* eslint-enable */

src/closure.js

@@ -5,12 +5,28 @@ 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.
+  let count = 0;
+  return {
+    increment: () => {
+      count++;
+      return count;
+    },
+    decrement: () => {
+      count--;
+      return count;
+    }
+  };
 };
 
 const limitFunctionCallCount = (cb, n) => {