key errors done

Author: RaihanSharif

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;
+}