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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[i]);
}

console.log(alphabetList);

<IPython.core.display.Javascript object>

What I Changed

I changed…

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

// Copy your previous code to built alphabetList here

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

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

console.log(alphabetList);


let letterNumber = 26

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

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

<IPython.core.display.Javascript object>

What I Changed

I added my alphabet list code. Changed alphabetList to alaphabetList.length so the loop would stop once there are no more letters. Changed letterNumber to alphabetList[i - 1] to make it the letter i corresponds to instead of a number. Had to add the [i - 1] to compensate for how the computer starts couting at 0. Added words and letterNumber variable to complete the sentence.

Segment 3: Odd Numbers

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

Code:

%%js

let odds = [];
let i = 1;

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

console.log(odds);

<IPython.core.display.Javascript object>

What I Changed

I changed the evens variable to odds and the i variable to 1. Changed even.push(i) to odds.push(i). Changed console.log(evens) to console.log(odds).

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 = 1

while (i <= 100) {
    numbers.push(i)
    i += 1
}
for (var i of numbers) {
    //% divides and looks at remainder
    if (numbers[i] % 5 === 0)
        newNumbers.push(numbers[i])
    else if (numbers[i] % 2 === 0)
        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,
         "Chicken Nuggies": 2.99}
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?
}

function calculatePrice(items){
    var num = 0;
    for(var i = 0; i < items.length; i++){
        num += menu[items[i]];
    }
    return num;
}

var items = ["burger", "fries", "drink", "Chicken Nuggies"];
var price = calculatePrice(items);

console.log("This is total price for your items - " + price)

<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)