London | 26-ITP-January | Laura C | Sprint 2 | Structuring and Testing Data

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

@@ -1,13 +1,35 @@
 // Predict and explain first...
 //  =============> write your prediction here
 
+// I predict this will throw a SyntaxError because
+// the variable 'str' is declared twice inside the function.
+
+
+
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
 
-function capitalise(str) {
-  let str = `${str[0].toUpperCase()}${str.slice(1)}`;
-  return str;
-}
+// function capitalise(str) {
+//   let str = `${str[0].toUpperCase()}${str.slice(1)}`;
+//   return str;
+// }
+
 
 // =============> write your explanation here
+
+// This code throws a SyntaxError: Identifier 'str' has already been declared.
+// The function parameter is named 'str', and inside the function
+// we try to declare another variable using 'let str'.
+// JavaScript does not allow redeclaring a variable
+// in the same scope.
+
+
 // =============> write your new code here
+function capitaliseFixed(str) {
+  let result = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return result;
+}
+
+console.log(capitaliseFixed("hello"));
+
+

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

@@ -3,18 +3,41 @@
 // Why will an error occur when this program runs?
 // =============> write your prediction here
 
+// I predict this will throw a SyntaxError because
+// the parameter 'decimalNumber' is redeclared
+// using const inside the function
+
+
 // 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
 
+// This code throws a SyntaxError: Identifier 'decimalNumber' has already been declared.
+// The function already has a parameter called 'decimalNumber'
+// Declaring 'const decimalNumber' inside the function
+// redeclares the same variable in the same scope,
+// which JavaScript does not allow.
+//
+// Also, console.log(decimalNumber) will cause a ReferenceError
+// because decimalNumber is not defined outside the function.
+
+
 // 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

@@ -5,16 +5,38 @@
 
 // =============> write your prediction of the error here
 
-function square(3) {
-    return num * num;
-}
+// I predict this will throw a SyntaxError because
+// a number (3) is used as a function parameter,
+// which is not allowed in JavaScript.
+
+// function square(3) {
+//     return num * num;
+// }
 
 // =============> write the error message here
 
+// SyntaxError: Unexpected number
+
 // =============> explain this error message here
 
+// This throws a SyntaxError: Unexpected number.
+// Function parameters must be valid variable names.
+// The number 3 is not a valid identifier, so JavaScript
+// cannot parse the function definition.
+
+// Also, the function uses 'num' inside the body,
+// but 'num' is not defined anywhere.
+
+
 // Finally, correct the code to fix the problem
 
 // =============> write your new code here
 
+function square(num) {
+    return num * num;
+}
+
+console.log(square(3));
+
+
 

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

@@ -2,13 +2,29 @@
 
 // =============> write your prediction here
 
-function multiply(a, b) {
-  console.log(a * b);
-}
+// I predict the result will not be displayed correctly.
+// The multiply function logs the result but does not return it,
+// so the template literal will receive undefined.
 
-console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
+// function multiply(a, b) {
+// console.log(a * b);
+// }
+
+// console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
 
 // =============> write your explanation here
 
+// The multiply function uses console.log to print the result,
+// but it does not return the value
+// When the function is used inside the template literal,
+// it returns undefined because functions return undefined
+// if there is no return statement.
+
+
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+function multiply(a, b) {
+  return a * b;
+}
+
+console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);

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

@@ -1,13 +1,27 @@
 // Predict and explain first...
 //  =============> write your prediction here
+// I think this might print undefined
+// The return statement looks separate from a + b,
+// so maybe the function is not actually returning the sum.
 
-function sum(a, b) {
-  return;
-  a + b;
-}
 
-console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
+// function sum(a, b) {
+//   return;
+//   a + b;
+// }
+//console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
 
 // =============> write your explanation here
+// The function has 'return;' on its own line.
+// When JavaScript sees return, it stops the function immediately.
+// That means 'a + b' never runs.
+// Because nothing is returned, the function returns undefined.
+
 // 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

@@ -3,22 +3,56 @@
 // Predict the output of the following code:
 // =============> Write your prediction here
 
-const num = 103;
+// I think the program will print 3 every time.
+// Even though different numbers are passed into the function,
+// the function is using the variable 'num', which is 103.
 
-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)}`);
+// 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)}`);
 
 // 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 is not using the number that is passed into it.
+// Instead, it always uses the global variable 'num'
+// which is set to 103.
+// The last digit of 103 is 3
+// so the function always returns 3.
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
 
+function getLastDigit(number) {
+  return number.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
+
+// The function was not working properly because it did not use
+// the number that was passed into it.
+// Instead, it used the global variable 'num',
+// which was always 103.
+// That is why it always returned 3.
+//
+// To fix the problem, I added a parameter to the function
+// and used that parameter to calculate the last digit
+

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

@@ -14,6 +14,9 @@
 // Then when we call this function with the weight and height
 // It should return their Body Mass Index to 1 decimal place
 
-function calculateBMI(weight, height) {
+function calculateBMI(weight, height) {const bmi = weight / (height * height);
+  return bmi.toFixed(1);
+}
+console.log(calculateBMI(70, 1.73));
+
     // return the BMI of someone based off their weight and height
-}

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

@@ -14,3 +14,11 @@
 // 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(str) {
+  const upper = str.toUpperCase();
+  const result = upper.replaceAll(" ", "_");
+  return result;
+}
+
+console.log(toUpperSnakeCase("hello there"));
+console.log(toUpperSnakeCase("lord of the rings"));

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

@@ -4,3 +4,28 @@
 // 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)
+    .padEnd(2, "0");
+
+  return `£${pounds}.${pence}`;
+}
+
+// test calls
+console.log(toPounds("399p")); // £3.99
+console.log(toPounds("50p"));  // £0.50
+console.log(toPounds("5p"));   // £0.05
+console.log(toPounds("100p")); // £1.00

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

@@ -19,16 +19,35 @@ function formatTimeDisplay(seconds) {
 // a) When formatTimeDisplay is called how many times will pad be called?
 // =============> write your answer here
 
+// pad is called 3 times.
+
+
 // 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
 
+// The value assigned to num the first time is 0.
+
+
 // c) What is the return value of pad is called for the first time?
 // =============> write your answer here
 
+// The return value is "00" because 0 becomes "0"
+// and padStart adds a leading zero.
+
+
 // 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
 
+// The value assigned to num the last time is 1,
+// because remainingSeconds is 1
+
+
 // e) What is the return value assigned to num when pad is called for the last time in this program?  Explain your answer
 // =============> write your answer here
+
+//The return value is "01" because 1 becomes "1"
+// when converted to a string, and padStart adds a leading zero.
+
+