1.js

// Predict and explain first...
// Why will an error occur when this program runs?
// I predict an error will occur when this program runs because the variable 'decimalNumber' is already declared inside the function 'convertToPercentage' and cannot be redeclared.

// Try playing computer with the example to work out what is going on
// When the 'function convertToPercentage(decimalNumber)' is created, Javascript already creates a variable called decimalNumber. then, inside the function, 'const decimalNumber = 0.5' tries to create another variable with the same name. This casues a syntax error because you cannot declare two variables with the same name in the same scope. 

// function convertToPercentage(decimalNumber) {
  // const decimalNumber = 0.5;
  // const percentage = `${decimalNumber * 100}%`;

  // return percentage;
// }

// console.log(decimalNumber);

// Write your explanation here
// I redelcared the parameter decimalNumber using const. 
// I tried to log decimalNumber outside its scope.
// The variables declared inside the function are not available outside unless they are returned.

// Finally, correct the code to fix the problem

function convertToPercentage(decimalNumber) {
  const percentage = `${decimalNumber * 100}%`;
  return percentage;
}

console.log(convertToPercentage(0.5)); // "50%"