Merge pull request #1 from karsevar/mason-karsevar

patpalmerston · web-flow · commit 1f5b35e8718b · 2019-06-12T10:21:15.000-07:00
JavaScript-II problem sets
diff --git a/assignments/array-methods.js b/assignments/array-methods.js
@@ -55,29 +55,104 @@ const runners = [{"id":1,"first_name":"Charmain","last_name":"Seiler","email":"c
 
 // ==== Challenge 1: Use .forEach() ====
 // The event director needs both the first and last names of each runner for their running bibs.  Combine both the first and last names into a new array called fullName. 
-let fullName = [];
+
+/*
+ the following code is inspired by the MDN example on forEach() and populating 
+ a new array with the method.
+
+ with map the code could have been:
+ const fullName = runners.forEach(runner => {
+	return fullName.push(runner.first_name + ' ' + runner.last_name);
+ });
+
+ But it seems that such a syntax doesn't work with this method.
+*/ 
+const fullName = []
+
+runners.forEach(runner => {
+	return fullName.push(runner.first_name + ' ' + runner.last_name);
+});
 console.log(fullName);
 
 // ==== Challenge 2: Use .map() ====
 // The event director needs to have all the runner's first names converted to uppercase because the director BECAME DRUNK WITH POWER. Convert each first name into all caps and log the result
-let allCaps = [];
+let allCaps = runners.map(runner => {
+	return runner.first_name.toUpperCase();
+});
 console.log(allCaps); 
 
 // ==== Challenge 3: Use .filter() ====
 // The large shirts won't be available for the event due to an ordering issue.  Get a list of runners with large sized shirts so they can choose a different size. Return an array named largeShirts that contains information about the runners that have a shirt size of L and log the result
-let largeShirts = [];
+let largeShirts = runners.filter(runner => {
+	return runner.shirt_size == 'L';
+});
 console.log(largeShirts);
 
 // ==== Challenge 4: Use .reduce() ====
 // The donations need to be tallied up and reported for tax purposes. Add up all the donations into a ticketPriceTotal array and log the result
-let ticketPriceTotal = [];
+let ticketPriceTotal = runners.reduce((acc, currentValue) => {
+	acc += currentValue.donation;
+	return acc; 
+}, 0);
 console.log(ticketPriceTotal);
 
 // ==== Challenge 5: Be Creative ====
 // Now that you have used .forEach(), .map(), .filter(), and .reduce().  I want you to think of potential problems you could solve given the data set and the 5k fun run theme.  Try to create and then solve 3 unique problems using one or many of the array methods listed above.
 
 // Problem 1
+// Getting the name and contact information of the largest doners. For now above 100 dollars.
+let largestDonations = runners.filter(runner => runner.donation >= 100).map(runner => {
+	return {'first_name': runner.first_name, 'last_name': runner.last_name, 'email': runner.email, 'donation': runner.donation};
+});
+console.log(largestDonations);
+
+/* 
+
+found out that writing arr.map(runner => {key: value}) confusions interpretor.
+you need to write object returns in .map() methods as:
+
+arr.map(runner => {
+	return {key: value};
+});
+
+*/
 
 // Problem 2
+// How many people wear 'L' T-shirts? With reduce:
+let largeCount = runners.reduce((count, currentValue) => {
+	if (currentValue.shirt_size === 'L') {
+		count += 1;
+		return count
+	}
+	return count
+}, 0)
+
+console.log(largeCount);
+// 6 // let's see if this is correct.
+
+let largeCountCheck = runners.filter(runner => {
+	return runner.shirt_size === 'L';
+})
+console.log(largeCountCheck.length);
+// console.log(largeCountCheck);
+// The reduce command was correct the answer was 6 in total.
+
+
+
+// Problem 3
+// What is the number of donation companies? 
+
+/* 
+
+Got the following code from:
+https://stackoverflow.com/questions/15052702/count-unique-elements-in-array-without-sorting
+
+It uses reduce to find and count the unique values in an array;
+
+*/
 
-// Problem 3
+let uniqShirtSizes = runners.map(runner => runner.shirt_size).reduce((acc, val) => {
+  acc[val] = acc[val] === undefined ? 1 : acc[val] += 1;
+  return acc;
+}, {});
+console.log(uniqShirtSizes);
diff --git a/assignments/callbacks.js b/assignments/callbacks.js
@@ -27,24 +27,42 @@ const items = ['Pencil', 'Notebook', 'yo-yo', 'Gum'];
 
 function getLength(arr, cb) {
   // getLength passes the length of the array into the callback.
+  return cb(arr.length);
 }
+// invocation getLength():
+getLength(items, length => console.log('The length of the array is: ', length));
 
 function last(arr, cb) {
   // last passes the last item of the array into the callback.
+  return cb(arr[arr.length - 1]);
 }
+// invocation last(): 
+last(items, last => console.log('The last item in the array is: ', last));
 
 function sumNums(x, y, cb) {
   // sumNums adds two numbers (x, y) and passes the result to the callback.
+  return cb(x + y);
 }
+//invocation sumNums():
+sumNums(1, 2, sum => console.log('The sum of the numbers is: ', sum));
 
 function multiplyNums(x, y, cb) {
   // multiplyNums multiplies two numbers and passes the result to the callback.
+  return cb(x * y);
 }
+//  invocation multiplyNums():
+multiplyNums(5, 2, function(product) {
+  console.log('The product of the numbers is: ', product); 
+});
 
 function 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 logic = list.includes(item);
+  return cb(logic);
 }
+// invocation contains():
+contains('Pencilly', items, truthy => console.log(truthy));
 
 /* STRETCH PROBLEM */
 
diff --git a/assignments/closure.js b/assignments/closure.js
@@ -1,5 +1,17 @@
 // ==== Challenge 1: Write your own closure ====
 // Write a simple closure of your own creation.  Keep it simple!
+const repeatName = (name) => {
+	return function() {
+		return name += ' ' + name;
+	}
+} 
+
+const name = repeatName('mason');
+console.log(name());
+console.log(name());
+console.log(name());
+// Interesting with each iteration the name printed to the console 
+// doubles inplace of increasing by only one.
 
 
 /* STRETCH PROBLEMS, Do not attempt until you have completed all previous tasks for today's project files */
@@ -8,14 +20,49 @@
 // ==== Challenge 2: Create a counter function ====
 const counter = () => {
   // Return a function that when invoked increments and returns a counter variable.
+  let count = 0;
+  return function() {
+  	return ++count;
+  }
 };
 // Example usage: const newCounter = counter();
 // newCounter(); // 1
 // newCounter(); // 2
 
+const newCounter = counter();
+
+console.log(newCounter());
+console.log(newCounter());
+console.log(newCounter());
+// Works perfectly!!! 
+
 // ==== Challenge 3: Create a counter function with an object that can increment and decrement ====
 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 = 1;
+
+  return {
+  	increment: function() {
+  		return ++count;
+  	},
+
+  	decrement: function() {
+  		return --count;
+  	}
+  }
 };
+
+const counterObject = counterFactory();
+console.log(counterObject.increment());
+console.log(counterObject.increment());
+console.log(counterObject.increment());
+console.log(counterObject.decrement());
+console.log(counterObject.decrement());
+console.log(counterObject.decrement());
+console.log(counterObject.increment());
+console.log(counterObject.increment());
+
+
+// The behavior seems a little weird will need to check the logic.
+
+
