layout: post title: 1.4 Correcting errors description: Practice with identifying and correcting code blocks type: ccc author: Safin Singh and Rohan Juneja permalink: /basics/js-debug hide: True —

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College Board Big Idea 1

Identifying and Correcting Errors (Unit 1.4)

Become familiar with types of errors and strategies for fixing them

  • Review CollegeBoard videos and take notes on blog
  • Complete assigned MCQ questions if applicable

Code Segments

Practice fixing the following code segments!

Segment 1: Alphabet List

Intended behavior: create a list of characters from the string contained in the variable alphabet

Code:

%%js

var alphabet = "abcdefghijklmnopqrstuvwxyz";
var alphabetList = [];

for (var i = 0; i < 26; i++) {
	alphabetList.push(alphabet.charAt(i));
}

console.log(alphabetList);

<IPython.core.display.Javascript object>

What I Changed

I changed and added alphabet.charAt into the alphabetList.push to creaye spaces inbetween each letter and seperate them by individual characters instead of just being the entire alphabet at once.

Segment 2: Numbered Alphabet

Intended behavior: print the number of a given alphabet letter within the alphabet. For example:

"_" is letter number _ in the alphabet

Where the underscores (_) are replaced with the letter and the position of that letter within the alphabet (e.g. a=1, b=2, etc.)

Code:

%%js


var alphabet = "abcdefghijklmnopqrstuvwxyz";
var alphabetList = [];

for (var i = 0; i < 26; i++) {
	alphabetList.push(alphabet.charAt(i));
}

console.log(alphabetList);
// Copy your previous code to built alphabetList here

let letterNumber = 5

for (var i = 0; i < alphabetList.length ; i++) {
	if (i === letterNumber-1) {
		console.log(alphabetList[letterNumber-1] + " is letter " + letterNumber + " in the alphabet")
	}
}

// Should output:
// "e" is letter number 5 in the alphabet

<IPython.core.display.Javascript object>

What I Changed

I changed…

Segment 3: Odd Numbers

Intended behavior: print a list of all the odd numbers below 10

Code:

%%js

let evens = [];
let i = 1;

while (i <= 10) {
  evens.push(i);
  i += 2;
}

console.log(evens);

<IPython.core.display.Javascript object>

What I Changed

I changed…

BELOW NOT EDITED

The intended outcome is printing a number between 1 and 100 once, if it is a multiple of 2 or 5

  • What values are outputted incorrectly. Why?
  • Make changes to get the intended outcome.
%%js

var numbers = []
var newNumbers = []
var i = 0

while (i < 100) {
    numbers.push(i)
    i += 1
}
for (var i of numbers) {
    if (numbers[i] % 5 === 0)
        newNumbers.push(numbers[i])
    if (numbers[i] % 2 === 0)
        newNumbers.push(numbers[i])
    if (numbers[i] % 5 != 5)
        newNumbers.push(numbers[i])
 }
console.log(newNumbers) 
    

<IPython.core.display.Javascript object>

Challenge

This code segment is at a very early stage of implementation.

  • What are some ways to (user) error proof this code?
  • The code should be able to calculate the cost of the meal of the user

Hint:

  • write a “single” test describing an expectation of the program of the program
  • test - input burger, expect output of burger price
  • run the test, which should fail because the program lacks that feature
  • write “just enough” code, the simplest possible, to make the test pass

Then repeat this process until you get program working like you want it to work.

%%js

var menu = {
    "burger": 3.99,
    "fries": 1.99,
    "drink": 0.99
};
var total = 0;

// Function to display the menu and calculate the cost of selected items
function calculateCost(item) {
    if (menu.hasOwnProperty(item)) {
        total += menu[item];
        console.log(item + " added to the order. Total cost: $" + total.toFixed(2));
    } else {
        console.log("Sorry, " + item + " is not on the menu.");
    }
}

// Test Case 1: Input "burger"
calculateCost("burger"); // This should add the price of the burger to the total and print the total cost.

// Display the updated total cost
console.log("Total cost of the meal: $" + total.toFixed(2));


<IPython.core.display.Javascript object>

Hacks

  • Fix the errors in the first three segments in this notebook and say what you changed in the code cell under “What I Changed” (Challenge is optional)