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Activity 4.4 — Processing Arrays

Introduction

Activity 4.4

Processing Data with Arrays

Topics

Processing arrays using traversal
Counting elements
Calculating totals and averages
Using conditionals with processed data

From Lists to Data

In the previous activity, arrays helped us store and display information.

In this activity, arrays become data — something we can analyze, summarize, and make decisions with.

The Processing Pattern

Processing an array usually follows this pattern:

Start with an accumulator variable (count, total)
Traverse the array
Update the accumulator each loop
Use the final result

Demo: Counting Items

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// Processing Pattern: Counting Elements
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let tasks = ["Homework", "Study", "Workout"];
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let count = 0;
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let i = 0;
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while (i < tasks.length) {
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  count++;
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  i++;
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}
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console.log("Number of tasks:", count);

Demo: Total & Average

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// Processing Pattern: Total + Average
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let scores = [85, 90, 78, 92, 88];
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let total = 0;
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let i = 0;
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while (i < scores.length) {
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  total += scores[i];
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  i++;
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}
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let average = total / scores.length;
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console.log("Average score:", average);

Why This Matters

This is how programs analyze survey results
This is how grades are summarized
This pattern appears directly in the Create Performance Task

'F' → Fullscreen

Objectives

Use traversal to process every element in an array.
Count elements using an accumulator variable.
Calculate totals and averages from numeric arrays.
Use conditionals based on processed results.

Activity Tasks

Create a new project named arrays-processing.
Complete each task individually.

Task 1: Task Counter

Use traversal to count how many tasks exist.
Store the result in a variable named count.

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console.log("--- Demo 1: Task Counter ---");
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// Starter task list
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let tasks = [
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  "Finish math homework",
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  "Practice arrays",
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  "Pack gym clothes",
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  "Email coach"
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];
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// Use traversal to COUNT how many tasks exist
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let count = 0;
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let i = 0;
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while (i < tasks.length) {
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  count++;
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  i++;
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}
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// Print the result
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console.log("You have " + count + " tasks to complete.");
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prompt("Press enter to continue...");

Task 2: Score Analyzer

Calculate the total and average of all scores.
Use an if/else statement with the average.

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console.log("--- Demo 2: Score Analyzer ---");
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// Starter data
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let scores = [72, 85, 90, 66, 88];
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// Step 1: Calculate the TOTAL of all scores
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let total = 0;
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let i = 0;
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while (i < scores.length) {
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  total += scores[i];
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  i++;
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}
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// Step 2: Calculate the AVERAGE score
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let average = total / scores.length;
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// Step 3: Print results
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console.log("Total score:", total);
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console.log("Average score:", average);
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// Step 4: Print a message based on the average
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if (average >= 70) {
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  console.log("Class average is passing.");
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} else {
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  console.log("Class average is not passing.");
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}
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prompt("Press enter to continue...");

Sample Output

Your program output should something similar to the sample output below.

--- Demo 1: Task Counter ---
You have 4 tasks to complete.
Press enter to continue... [Enter]

--- Demo 2: Score Analyzer ---
Total score: 401
Average score: 80.2
Class average is passing.
Press enter to continue... [Enter]

Reflection Questions

You may write your reflection answers as comments at the bottom of your code.

What is the purpose of an accumulator variable?
Why do we divide by array.length when calculating an average?
How does traversal allow a program to analyze data?

Submission

Submit your activity and reflection answers to the appropriate dropbox.