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 < 10; i++) {
	alphabetList.push(alphabet[i]);
}

console.log(alphabetList);

What I Changed

I changed the alphabetList.push command to push the first “i”(i being 10) letters of the alphabet instead of literally pushing “i” into alphabetList.

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 < 10; i++) {
    alphabetList.push(alphabet[i]);
}

console.log(alphabetList);

let letterNumber = 4;

for (var i = 0; i < alphabetList.length; i++) { // Use .length to get the length of the array
    if (i === letterNumber) {
        console.log(alphabetList[i] + " is letter number " + (i+1) + " in the alphabet"); // Use (i + 1) to get the correct letter number
    }
}


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

What I Changed

I changed the second for command to use the length of the alphabetList array rather than the array itself. I also changed the console.log command to print “i+1” because the array starts at 0 to get the correct number. Additionally, I had to change the let letterNumber = 5 to 4 for the same reason.

Segment 3: Odd Numbers

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

Code:

%%js

let evens = [];
let num = 0;

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

console.log(evens);

What I Changed

I changed the variable i to numbers because i has already been decalred earlier in the code, meaning we can’t use it again. By changing the variable to num, we can now decale num to be the array of even numbers.

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])
}
console.log(newNumbers) 

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

//shows the user the menu and prompts them to select an item
console.log("Menu")
for (var item in menu) {
    console.log(item + "  $" + menu[item].toFixed(2)) //why is toFixed used?
}
//ideally the code should support mutliple items
var item = "burger"

//code should add the price of the menu items selected by the user 
console.log(total)

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)