Complete Sprint 3 section 2: debug

Author: BrianY315

Sprint-3/2-mandatory-debug/0.js

@@ -1,14 +1,23 @@
 // Predict and explain first...
 
-// =============> write your prediction here
+// Prediction: The multiplication itself prints 320, but the template string
+// then shows undefined because multiply does not return the result.
 
-function multiply(a, b) {
+function multiplyBeforeFix(a, b) {
   console.log(a * b);
 }
 
+console.log(`The result of multiplying 10 and 32 is ${multiplyBeforeFix(10, 32)}`);
+
+function multiply(a, b) {
+  return a * b;
+}
+
 console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
 
-// =============> write your explanation here
+// Observed before the fix: 320, then "undefined" in the template string.
+// Explanation: console.log displays the product but returns undefined. The
+// function call inside the template string therefore evaluates to undefined.
 
 // Finally, correct the code to fix the problem
-//  =============> write your new code here
+// The corrected function above returns the product for the template string.

Sprint-3/2-mandatory-debug/1.js

@@ -1,13 +1,22 @@
 // Predict and explain first...
-//  =============> write your prediction here
+// Prediction: The output will say undefined because return exits the function
+// before the addition expression can run.
 
-function sum(a, b) {
+function sumBeforeFix(a, b) {
   return;
   a + b;
 }
 
+console.log(`The sum of 10 and 32 is ${sumBeforeFix(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
+// Observed before the fix: undefined.
+// Explanation: A newline immediately after return ends the return statement.
+// The function returns undefined and the following expression is unreachable.
 // Finally, correct the code to fix the problem
-//  =============> write your new code here
+// The corrected function above returns the sum.

Sprint-3/2-mandatory-debug/2.js

@@ -1,24 +1,32 @@
 // Predict and explain first...
 
 // Predict the output of the following code:
-// =============> Write your prediction here
+// Prediction: Each line reports 103's last digit (3), because getLastDigit
+// ignores its arguments and always reads the global num variable.
 
 const num = 103;
 
-function getLastDigit() {
+function getLastDigitBeforeFix() {
   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 ${getLastDigitBeforeFix(42)}`);
+console.log(`The last digit of 105 is ${getLastDigitBeforeFix(105)}`);
+console.log(`The last digit of 806 is ${getLastDigitBeforeFix(806)}`);
 
 // Now run the code and compare the output to your prediction
-// =============> write the output here
+// Output: Each line reports 3.
 // Explain why the output is the way it is
-// =============> write your explanation here
+// Explanation: getLastDigit has no parameter and reads the unchanged global
+// num (103), so passing 42, 105, or 806 has no effect.
 // 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