diff --git a/exercises/A-setup-ide/README.md b/exercises/A-setup-ide/README.md
index 1412871b6..de230419b 100644
--- a/exercises/A-setup-ide/README.md
+++ b/exercises/A-setup-ide/README.md
@@ -2,12 +2,12 @@ There are some tools that will help you to write code. One of these, [Prettier](
 
 ### 1. Install prettier
 
-* In Visual Studio open the extensions panel (see https://code.visualstudio.com/docs/editor/extension-gallery#_browse-and-install-extensions)
-* Search for `Prettier - Code formatter`
-* Click install on the top result
+- In Visual Studio open the extensions panel (see https://code.visualstudio.com/docs/editor/extension-gallery#_browse-and-install-extensions)
+- Search for `Prettier - Code formatter`
+- Click install on the top result
 
 ### 2. Enable formatting on save
 
-* In Visual Studio open the settings file (see https://code.visualstudio.com/docs/getstarted/settings#_creating-user-and-workspace-settings)
-* Search for `editor format`
-* Set `editor.formatOnSave` and `editor.formatOnPaste` to true
+- In Visual Studio open the settings file (see https://code.visualstudio.com/docs/getstarted/settings#_creating-user-and-workspace-settings)
+- Search for `editor format`
+- Set `editor.formatOnSave` and `editor.formatOnPaste` to true
diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..1093e3b6c 100644
--- a/exercises/B-hello-world/exercise.js
+++ b/exercises/B-hello-world/exercise.js
@@ -1 +1,12 @@
 console.log("Hello world");
+console.log('\n' + "Hello world, I just started learning JavaScript!");
+
+var name = 'Liew';
+var num = 1234;
+var quote = ' is learning JavaScript!';
+var noQuoteMark = testing;
+
+console.log('\n' + name + ' ' + num + quote);
+console.log('\n' + 12345678);
+
+console.log(noQuoteMark); //uncaught Reference Error: testing is not defined
\ No newline at end of file
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..8cfe874e1 100644
--- a/exercises/C-variables/exercise.js
+++ b/exercises/C-variables/exercise.js
@@ -1,3 +1,7 @@
 // Start by creating a variable `greeting`
 
+let greeting = 'Hello World!';
+
+console.log(greeting);
+console.log(greeting);
 console.log(greeting);
diff --git a/exercises/D-strings/exercise.js b/exercises/D-strings/exercise.js
index 2cffa6a81..7f59514df 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,13 @@
 // Start by creating a variable `message`
+var message = 'This is a string';
+
+var messageType = typeof message;
+
+var testNum = 123456;
+var testNumType = typeof testNum;
 
 console.log(message);
+console.log(messageType);
+
+console.log('\n' + testNum);
+console.log(testNumType);
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..2a0f74566 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,6 @@
 // Start by creating a variable `message`
 
-console.log(message);
+var greeting = 'Hello, my name is ';
+var name = 'Liew';
+
+console.log(greeting + name);
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..bc3544595 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,11 @@
 // Start by creating a variable `message`
+var name = 'Liew';
+var nameLength = name.length;
+var nameLowerCase = name.toLowerCase();
+var nameExtraWhiteSpace = '      Liew';
+
+console.log('My name is ' + name + ' and my name is ' + nameLength + ' characters long');
+console.log('My name is ' + nameLowerCase + ' and my name is ' + nameLength + ' characters long');
+console.log('My name is ' + nameExtraWhiteSpace.trim() + ' and my name is ' + nameLength + ' characters long');
+
 
-console.log(message);
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..679ab8b04 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,4 @@
-const name = " Daniel  ";
+const name = " Liew  ";
+let nameLength = name.length;
 
-console.log(message);
+console.log('My name is ' + name.trim() + ' and my name is ' + nameLength + ' characters long');
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..a8e6b3dc2 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,9 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+let numberOfStudents = 40;
+let numberOfMentors = 10;
+
+let sum = numberOfStudents + numberOfMentors;
+
+console.log('Number of students: ' + numberOfStudents);
+console.log('Number of mentors: ' + numberOfMentors);
+console.log('Total number of students and mentors ' + sum);
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..21de86352 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,9 @@
 var numberOfStudents = 15;
 var numberOfMentors = 8;
+
+let sum = numberOfStudents + numberOfMentors;
+let percentageOfStudents = numberOfStudents / sum * 100;
+let percentageOfMentors = numberOfMentors / sum * 100;
+
+console.log('Percentage students: ' + Math.round(percentageOfStudents) + '%');
+console.log('Percentage mentors: ' + Math.round(percentageOfMentors) + '%');
\ No newline at end of file
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..cd3689c61 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,7 +1,17 @@
 function halve(number) {
   // complete the function here
+  return number / 2;
 }
 
 var result = halve(12);
+let a = halve(15);
+let b = halve(202);
+let c = halve(99.5);
+let d = halve(15.6);
 
 console.log(result);
+console.log(a);
+console.log(b);
+console.log(c);
+console.log(d);
+console.log(Math.round(d));
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..d29e195d9 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,5 +1,6 @@
 function triple(number) {
   // complete function here
+  return number * 3
 }
 
 var result = triple(12);
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..dbd50454d 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,6 +1,7 @@
 // Complete the function so that it takes input parameters
-function multiply() {
+function multiply(a, b) {
   // Calculate the result of the function and return it
+  return a * b;
 }
 
 // Assign the result of calling the function the variable `result`
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..937d62c46 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,4 +1,7 @@
 // Declare your function first
+function divide (a, b){
+    return a / b;
+}
 
 var result = divide(3, 4);
 
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..aa39259a2 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,4 +1,8 @@
 // Write your function here
+function createGreeting (name){
+    return 'Hello, my name is ' + name;
+}
+
 
 var greeting = createGreeting("Daniel");
 
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..8ef1c3bae 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,10 @@
 // Declare your function first
+function addison (a, b){
+    return a + b;
+};
 
 // Call the function and assign to a variable `sum`
 
+let sum = addison(13, 124);
+
 console.log(sum);
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..e6d6c20ed 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,4 +1,8 @@
 // Declare your function here
+function createLongGreeting (name, age){
+    return 'Hello, my name is ' + name + ' and I\'m ' + age + ' years old';
+}
+
 
 const greeting = createLongGreeting("Daniel", 30);
 
diff --git a/exercises/L-functions-nested/exercise.js b/exercises/L-functions-nested/exercise.js
index a5d377442..ef1228159 100644
--- a/exercises/L-functions-nested/exercise.js
+++ b/exercises/L-functions-nested/exercise.js
@@ -1,5 +1,57 @@
+// ***** test out the example
+// function getAgeInDays(age) {
+//   return age * 365;
+// }
+
+// function createCreeting(name, age) {
+//   var ageInDays = getAgeInDays(age);
+//   var message =
+//     "My Name is " + name + " and I was born over " + ageInDays + " days ago!";
+//   return message;
+// }
+
+// let test = createCreeting('Liew', 999);
+
+// console.log(test);
+
+// Exercise 1
+console.log('Exercise 1:' + '\n');
+function calPercentage (num1, num2){
+    return Math.floor(num1/(num1 + num2) * 100);
+}
+
+function greeting (category, percentage){
+    return 'Percentage ' + category + ': ' + percentage + '%';
+}
+
+let students = 15;
+let mentors = 8;
+let percentageOfStudents = calPercentage (students, mentors);
+let percentageOfMentors = calPercentage (mentors, students);
+
+console.log (greeting('students', percentageOfStudents));
+console.log (greeting('mentors', percentageOfMentors));
+
+// Exercise 2
+console.log('\n************************' + '\n' + 'Exercise 2:' + '\n');
+
 var mentor1 = "Daniel";
 var mentor2 = "Irina";
 var mentor3 = "Mimi";
 var mentor4 = "Rob";
 var mentor5 = "Yohannes";
+
+function changeToUpperCase (name){
+    return name.toUpperCase();
+}
+
+function greetingShout (mentor){
+    return 'HELLO ' + changeToUpperCase(mentor);
+}
+
+console.log(greetingShout(mentor1));
+console.log(greetingShout(mentor2));
+console.log(greetingShout(mentor3));
+console.log(greetingShout(mentor4));
+console.log(greetingShout(mentor5));
+
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index 70a2fe863..aac064e64 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,7 +5,9 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(usDollar) {
+  return usDollar * 1.4;
+}
 
 /*
   CURRENCY FORMATTING
@@ -15,7 +17,9 @@ function convertToUSD() {}
   They have also decided that they should add a 1% fee to all foreign transactions, which means you only convert 99% of the £ to BRL.
 */
 
-function convertToBRL() {}
+function convertToBRL(brazilianReal) {
+  return brazilianReal * 5.7 * 0.99;
+}
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/extra/2-piping.js b/extra/2-piping.js
index 067dd0f5b..632b9bb7d 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,28 @@
   the final result to the variable goodCode
 */
 
-function add() {
-
+function add(num1, num2) {
+    return num1 + num2;
 }
 
-function multiply() {
-
+function multiply(num1, num2) {
+    return num1 * num2;
 }
 
-function format() {
-
+function format(num) {
+    return '£' + num;
 }
 
 const startingValue = 2
 
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode = 
+let badCode = format(multiply(add(startingValue, 10), 2));
 
 /* BETTER PRACTICE */
 
-let goodCode = 
+let addition = add(startingValue, 10);
+let multiplication = multiply (addition, 2);
+let goodCode = format(multiplication);
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index 0a21afd1b..46cf52eec 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,16 @@
 // There are syntax errors in this code - can you fix it to pass the tests?
 
-function addNumbers(a b c) {
+function addNumbers(a, b, c) {
     return a + b + c;
 }
 
-function introduceMe(name, age)
-return "Hello, my name is " + name "and I am " age + "years old";
+function introduceMe(name, age){
+    return "Hello, my name is " + name + " and I am " + age + " years old";
+}
 
 function getTotal(a, b) {
-    total = a ++ b;
-
-    return "The total is total"
+    total = a + b;
+    return "The total is " + total;
 }
 
 /* 
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 3c578ad87..1f1245b39 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,15 @@
 // The syntax for this function is valid but it has an error, find it and fix it.
 
 function trimWord(word) {
-  return wordtrim();
+  return word.trim();
 }
 
 function getWordLength(word) {
-  return "word".length();
+  return word.length;
 }
 
 function multiply(a, b, c) {
-  a * b * c;
-  return;
+  return a * b * c;
 }
 
 /* 
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index c9221a200..7535e8ec1 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,9 +1,15 @@
 // Add comments to explain what this function does. You're meant to use Google!
+// below is a function which return a random number between >= 0 and < 10, due to the multiplication of 10. 
+// Math.random is a function returns a floating-point, pseudo-random number in the range 0 to less than 1 (inclusive of 0, but not 1)
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random
 function getNumber() {
   return Math.random() * 10;
 }
 
+
 // Add comments to explain what this function does. You're meant to use Google!
+//concat() is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat
 function s(w1, w2) {
   return w1.concat(w2);
 }
@@ -11,6 +17,7 @@ function s(w1, w2) {
 function concatenate(firstWord, secondWord, thirdWord) {
   // Write the body of this function to concatenate three words together.
   // Look at the test case below to understand what this function is expected to return.
+  return firstWord + " " + secondWord + " " + thirdWord;
 }
 
 /* 
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index c9e41c691..a1b3a01ee 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,9 @@
   Sales tax is 20% of the price of the product
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(price) {
+  return price * 1.2;
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +19,9 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(price) {
+  return '£' + calculateSalesTax(price).toFixed(2);
+}
 
 /* 
 ===================================================