mandatory-debug done

Author: RaihanSharif

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