Read & Predict

One of the most important programming skills is being able to read code before writing code. Professional developers spend much more time reading code than typing it.

In this activity, you will analyze a JavaScript function, predict what it does, and then verify whether your prediction was correct.

Learning Objectives

By the end of this activity, you should be able to:

• Read a JavaScript function from top to bottom.
• Identify the purpose of an if statement.
• Follow the flow of execution.
• Predict a function's return value.
• Verify your prediction by running the code.

The Big Idea

Code to Analyze

function calculateTotal(bill, tipPercent) {
    if (bill < 0) {
        return "Invalid bill";
    }

    let tip = bill * (tipPercent / 100);

    return bill + tip;
}

calculateTotal(100, 10);

Instructions

Questions

Answer the following before running the program.

1. What value does calculateTotal(100, 10) return?
2. What happens if bill is -5?
3. Which line prevents invalid bills?
4. Identify:
   • the function
   • the if statement
   • the variable
   • the mathematical calculation

Reflection

After verifying your answers, write a short reflection.

• Were your predictions correct?
• What surprised you?
• What did you learn about how JavaScript functions execute?

Expected Output

By the end of the activity, you should have:

• A completed prediction log.
• Verified answers after running the code.
• A short reflection explaining what you learned.

Submission

Submit a document containing:

1. Your answers to the four questions.
2. The actual output after running the program.
3. Your reflection describing whether your prediction was correct.

Grading Rubric