London | 26-ITP-May | Raihan Sharif | Sprint 2 | Coursework

Sprint-2/1-key-errors/0.js

@@ -1,5 +1,8 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// the str variable declaration inside of the function shadows the function parameter
+// if an empty string is passed to the function, trying to access element at index 0, and calling
+// toUpperCase() on it will cause an error, as that value would be undefined.
 
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
@@ -10,4 +13,12 @@ function capitalise(str) {
 }
 
 // =============> write your explanation here
+// Error message is:
+//SyntaxError: Identifier 'str' has already been declared
+// it means that JavaScript has already declared a variable name 'str' within the function's scope.
+// so when you try to declare it in the body of the function, there's a naming conflict.
+
 // =============> write your new code here
+function capitalise2(str) {
+  return `${str[0].toUpperCase()}${str.slice(1)}`;
+}

Sprint-2/1-key-errors/1.js

@@ -2,19 +2,32 @@
 
 // Why will an error occur when this program runs?
 // =============> write your prediction here
+// First, it's trying to print decimalNumber, an undeclared value.
+// Second, the decimalNumber variable name is already taken when it tries to declare it in the first
+// line of the function body.
 
 // Try playing computer with the example to work out what is going on
 
-function convertToPercentage(decimalNumber) {
-  const decimalNumber = 0.5;
-  const percentage = `${decimalNumber * 100}%`;
+// function convertToPercentage(decimalNumber) {
+//   const decimalNumber = 0.5;
+//   const percentage = `${decimalNumber * 100}%`;
 
-  return percentage;
-}
+//   return percentage;
+// }
 
-console.log(decimalNumber);
+// console.log(decimalNumber);
 
 // =============> write your explanation here
+// when Javascript reads the function definition, and sees a parameter, it creates a variable with that name
+// scoped to the body of the function. Then when it reads the first line within the body, the 'decimalNumber'
+// name is already taken.
 
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+function convertToPercentage(decimalNumber) {
+  const percentage = `${decimalNumber * 100}%`;
+
+  return percentage;
+}
+
+console.log(convertToPercentage(0.5));

Sprint-2/1-key-errors/2.js

@@ -1,20 +1,23 @@
-
 // Predict and explain first BEFORE you run any code...
 
 // this function should square any number but instead we're going to get an error
 
 // =============> write your prediction of the error here
+// the function parameter cannot be a number, or start with a number, follows same rules as variable names
+// num is undefined.
 
-function square(3) {
-    return num * num;
-}
+// function square(3) {
+//     return num * num;
+// }
 
 // =============> write the error message here
+//SyntaxError: Unexpected number
 
 // =============> explain this error message here
+// function parameter is a number, which is not a valid type for parameters
 
 // Finally, correct the code to fix the problem
 
-// =============> write your new code here
-
-
+function square(num) {
+  return num * num;
+}

Sprint-2/2-mandatory-debug/0.js

@@ -1,14 +1,28 @@
 // Predict and explain first...
 
 // =============> write your prediction here
+// logging the result of the function will always be undefined, since it doesn't return anything.
+// if the inputs are two numbers, should console log the right number, e.g. (2, 2) -> 4 (2.5, 2.5) -> 6.25
+// otherwise, it might produce incorrect results
 
-function multiply(a, b) {
-  console.log(a * b);
-}
+// function multiply(a, b) {
+//   console.log(a * b);
+// }
 
-console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
+// console.log(`The result of multiplying 10 and 32 is ${multiply(2, "asdf")}`);
 
 // =============> write your explanation here
+// Javascript tries to cast non-number values to numbers before multiplying. So, "3" to 3 for example.
+// if the value can't be converted to a number, it might cause unpredictable or incorrect outputs.
+// e.g. Boolean true is converted to numeric 1, so true * 2 becomes 1 * 2 = 2.
 
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function multiply(a, b) {
+  if (Number.isFinite(a) && Number.isFinite(b)) {
+    return a * b;
+  }
+  throw new TypeError("Arguments must be finite numbers");
+}
+
+console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);

Sprint-2/2-mandatory-debug/1.js

@@ -1,13 +1,23 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// the output of console log should be 'The sub of 10 and 32 is undefined'
 
-function sum(a, b) {
-  return;
-  a + b;
-}
+// function sum(a, b) {
+//   return;
+//   a + b;
+// }
 
-console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
+// console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
 
 // =============> write your explanation here
+// since the return statement is the first thing in the function body, and it returns nothing.
+// the return value of the function is undefined.
+// so in the console log, it will coerce undefined to string, and print that.
+
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function sum(a, b) {
+  return a + b;
+}
+
+console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);

Sprint-2/2-mandatory-debug/2.js

@@ -2,23 +2,40 @@
 
 // Predict the output of the following code:
 // =============> Write your prediction here
+// The output will always be 3
 
 const num = 103;
 
-function getLastDigit() {
-  return num.toString().slice(-1);
-}
+// function getLastDigit() {
+//   return num.toString().slice(-1);
+// }
 
-console.log(`The last digit of 42 is ${getLastDigit(42)}`);
-console.log(`The last digit of 105 is ${getLastDigit(105)}`);
-console.log(`The last digit of 806 is ${getLastDigit(806)}`);
+// console.log(`The last digit of 42 is ${getLastDigit(42)}`);
+// console.log(`The last digit of 105 is ${getLastDigit(105)}`);
+// console.log(`The last digit of 806 is ${getLastDigit(806)}`);
 
 // Now run the code and compare the output to your prediction
 // =============> write the output here
+// The last digit of 42 is 3
+// The last digit of 105 is 3
+// The last digit of 806 is 3
+
 // Explain why the output is the way it is
 // =============> write your explanation here
+// The function does not take an argument, so supplying one is no use.
+// Since there is no num variable inside the function, it looks for it in the nearest enclosing scope.
+// It finds num = 103, so it will always operate on that variable
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+function getLastDigit(num) {
+  return num.toString().slice(-1);
+}
+
+console.log(`The last digit of 42 is ${getLastDigit(42)}`);
+console.log(`The last digit of 105 is ${getLastDigit(105)}`);
+console.log(`The last digit of 806 is ${getLastDigit(806)}`);
 
 // This program should tell the user the last digit of each number.
 // Explain why getLastDigit is not working properly - correct the problem
+// ??? it returns the last digit

Sprint-2/3-mandatory-implement/1-bmi.js

@@ -15,5 +15,5 @@
 // It should return their Body Mass Index to 1 decimal place
 
 function calculateBMI(weight, height) {
-    // return the BMI of someone based off their weight and height
-}
+  return (weight / height ** 2).toFixed(1);
+}

Sprint-2/3-mandatory-implement/2-cases.js

@@ -14,3 +14,9 @@
 // You will need to come up with an appropriate name for the function
 // Use the MDN string documentation to help you find a solution
 // This might help https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toUpperCase
+
+function toUpperSnakeCase(inputStr) {
+  return inputStr.toUpperCase().replaceAll(" ", "_");
+}
+
+console.log(toUpperSnakeCase("hello there"));

Sprint-2/3-mandatory-implement/3-to-pounds.js

@@ -4,3 +4,27 @@
 // You will need to declare a function called toPounds with an appropriately named parameter.
 
 // You should call this function a number of times to check it works for different inputs
+
+function toPounds(penceString) {
+  const penceStringWithoutTrailingP = penceString.substring(
+    0,
+    penceString.length - 1
+  );
+
+  const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+  const pounds = paddedPenceNumberString.substring(
+    0,
+    paddedPenceNumberString.length - 2
+  );
+
+  const pence = paddedPenceNumberString.substring(
+    paddedPenceNumberString.length - 2
+  );
+
+  return `£${pounds}.${pence}`;
+}
+
+console.log(toPounds("399p"));
+console.log(toPounds("9p"));
+console.log(toPounds("20p"));
+console.log(toPounds("1220p"));

Sprint-2/4-mandatory-interpret/time-format.js

@@ -11,24 +11,29 @@ function formatTimeDisplay(seconds) {
   return `${pad(totalHours)}:${pad(remainingMinutes)}:${pad(remainingSeconds)}`;
 }
 
+console.log(formatTimeDisplay(61));
+
 // You will need to play computer with this example - use the Python Visualiser https://pythontutor.com/visualize.html#mode=edit
 // to help you answer these questions
 
 // Questions
 
 // a) When formatTimeDisplay is called how many times will pad be called?
-// =============> write your answer here
+// 3
 
 // Call formatTimeDisplay with an input of 61, now answer the following:
 
 // b) What is the value assigned to num when pad is called for the first time?
-// =============> write your answer here
+// 0
 
 // c) What is the return value of pad is called for the first time?
-// =============> write your answer here
+// "00"
 
 // d) What is the value assigned to num when pad is called for the last time in this program?  Explain your answer
-// =============> write your answer here
+// value assigned is 1, because pad is called with remainingSeconds as the argument.
+// remainingSeconds is the remainder of 61 divided by 60, which is 1.
 
 // e) What is the return value of pad when it is called for the last time in this program?  Explain your answer
-// =============> write your answer here
+// return value is "01". First, the pad function converts input num to string so the return type is string.
+// Second, the function pads the start of the string with up to two "0" characters, and in this case
+// since num is a single character, it only pads one "0" at the start.