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LAB 04 –HTML+JS+ComputationalThinking

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EECS 1012: LAB 04 –HTML+JS+ComputationalThinking
A. REMINDERS
1) You should attend your own lab session (the one you are enrolled in). If you need to change your lab
enrollment, you should go to the department. Instructors or TAs cannot change your enrollment. TAs are
available via Zoom to help you during your lab hours.
2) You are required to pass the pre-lab mini quiz posted on eClass not later than the first 10 minutes of your
lab time. You should study the recent course materials and corresponding links/hints and Section B of this
document, as well as working on at least first tasks of this lab before trying the prelab quiz. You have 4
attempts; and you need at least 80% to pass. However, each time you may get some different questions.
You should try your first attempt at least one day before your deadline so that, if needed, you have time to
(re)study the materials for your next attempts. Failing the pre-lab mini quiz is equal to failing the whole lab,
yet you are still highly encouraged to complete the lab and submit your work to eClass.
3) You can also have your work verified and graded during the lab sessions. Feel free to signal a TA for help if
you stuck on any of the steps below. Yet, note that TAs would need to help other students too.
4) You can submit your lab work in eClass any time before 21:00 on Wednesday of the week the lab is for. In
order to pass this lab, your grade in it should be at least 70%.
B. IMPORTANT PRE-LAB WORKS YOU NEED TO DO BEFORE GOING TO THE LAB
1) Download this lab files and read them carefully to the end.
2) You should have a good understanding of
• Events (such as onclick) and event handlers
• document.getElementById().innerHTML
• js functions such as parseInt(), parseFloat(), toFixed()
• the if statement and switch statement in js
• memory space (aka variable), js operators such as “+” and the concept of overloading
• flowchart symbols as described in the lecture notes
3) Practice drawing flowchart symbols in draw.io or MS Word or PowerPoint. If you plan to draw your
flowcharts on paper, please make sure you have pencils, erasers, and perhaps a ruler.
C. GOALS/OUTCOMES FOR LAB
• To practice computational thinking by first drawing flowcharts for basic computation
problems, followed by implementation in JS
D. TASKS
1) Your first and major task in this lab is to design eight algorithms and draw the corresponding flowcharts. This
task must be done in teams of two. (By the permission of your Lab TA, only one team can have three
members if the lab population is odd.) While you are done, you should show your flowcharts to the TAs
before you go to next part. The TA may ask you to make minor modifications to your flowcharts to
demonstrate your computational thinking skills in those contexts.
• Note you should NOT open VS-Code or browsers before finishing Task 1. You can draw your
flowcharts on paper or draw them in draw.io or in MS Word or PowerPoint.
2) Then, you are provided with ct.html document and supporting files such as ct.css and ct.js. Your
task is to translate your first 5 flowcharts to js.
3) You will generate at least five html and js files in this process. You should demo each HTML file to the TA.
For that, please, have each html file open in a different tab so you can show the progression.
4) See next pages for details on how to modify your html and js files.
E. SUBMISSIONS
1) Manual verification by a TA
You may want to have your TA verifying your lab before submission. The TA will look at your various files in
their progression. The TA may also ask you to make minor modifications to the lab to demonstrate your
knowledge of the materials. The TA can then record your grade in the system.
2) eClass submission
You will see an assignment submission link on eClass. Create a folder named “Lab04” and copy all of your lab
materials inside (img_{01,02,03,04,05,06,07,08.jpg, ct_Ex{1,2,3,4,5}.html and
ct_Ex{1,2,3,4,5}.js). This folder should be compressed (or tar.gz) and the compressed file submitted.
Make sure size of each image file is not more than 1MB, otherwise you may not be able to upload your work.
F. COMPUTATIONAL THINKIG
Part 1: This part must be done in teams of two. (By the permission of the TA, only one team can have three
members if the lab population is odd.) If you have done it at home, you are required to discuss it with a peer from
your lab before you show your final solution to your TA.
Using a computer program (or on paper), draw the following flowcharts and write your name on each. By end of this
lab, you should take a screenshot (or a picture) from each flowchart and both you and your teammate should submit
them to eClass as img_{01,02,03,04,05,06,07,08}.jpg files, where img_x is the flowchart for exercise x below. Make
sure the size of each image is less than 500KB, e.g. by reducing the resolution of your camera.
IMPORTANT: You are required to use the symbols introduced in the lecture which are inspired from this book
(“Computer Science: a first course” by Forsythe, Keenan, Organick, Stenberg)
IMPORTANT: You are required to provide preconditions and postconditions for each solution you provide.
Ex 1) draw a flowchart for a computer program to receive two numbers and output their sum.
Ex 2) draw a flowchart for a computer program to receive three numbers and store them in memory spaces
called a, b, and c as three sides of a triangle and, by using Heron’s formula, calculate and output the area
of the triangle. You may need to refresh your memory or learn about Heron’s formula by visiting
https://www.mathopenref.com/heronsformula.html
Ex 3) draw a flowchart for a computer program to receive three numerical coefficients of a quadratic equation
(store them in memory spaces called a, b, and c) and calculate and output its roots. Write a precondition
that assumes coefficients are good enough such that a solution in real number exists. That means your
design should not concern cases for which a solution does not exist. If you need to refresh your memory
on this topic, this might be a good source: https://www.mathsisfun.com/algebra/quadratic-equation.html
Ex 4) draw a flowchart to receive three numerical coefficients of a quadratic equation and determines if it has
two distinct real roots, one root, or no roots in real numbers. This page might be a good reference:
https://www.math10.com/en/algebra/quadratic-equation.html
Ex 5) draw a flowchart to receive a number and map it to a letter grade based on York standard. You may need
to look at this reference: http://calendars.registrar.yorku.ca/2012-2013/academic/grades/index.htm
Assume if the grade is 40 to 49, it’s mapped to E.
Ex 6) assume there is a webpage containing an HTML input of type text and a button. When the button is
clicked a function, named Problem06, is called. Draw a flowchart that outputs whether the input is
positive or negative until a zero is received. When a zero is received, the button is disabled (so the
function cannot be called anymore).
Ex 7) by modifying your flowchart above, draw a flowchart to continue receiving numbers and output if they
are positive or negative until a zero is entered. When a zero is entered, the program should output how
many positive and how many negative numbers have been entered, then it stops.
Ex 8) considering the same approach above, draw a flowchart to continue receiving numbers and output if they
are divisible by 6 or not until a zero is entered. When a zero is entered, the program should output how
many of the entered numbers were divisible by 6, then it stops. IMPORTANT RESTRICTION: you are not
allowed to divide the number by 6; therefore, you are not allowed to use the modulus operator (%) over
6 to verify the remainder whether the number is divided by 6. You can do any other math trick you wish.
Part 2: you are given ct.html, ct.css, ct.js files. Reading these files carefully in order to enhance your
learning before doing the following exercises.
Exercise 1. Copy ct.html to a new file named ct_Ex1.html. Copy ct.js to a new file named ct_Ex1.js.
Launch ct_Ex1.html with your browser and enter two numbers and click on the “enter” button, nothing
happens. In this exercise, you would modify the code such that it runs properly:
Make three changes to ct_Ex1.html, as follows:
1) Connect it to ct_Ex1.js by adding a link in the head element.
2) Add an event to the button such that when it’s clicked you handle that event by the add() function
in your js file.
3) Add your name to the list of authors of this page.
Launch ct_Ex1.html with your browser and enter 15 and 9. You should see the following result:
That is because the variables w and h in your js function are from data type “string”. The data type
variables in js are determined by the data type of the expression that is on the right side of the
assignment. In this case, because the data type of property value of the html object that the
getElementById returns is “string”, therefore the data type of w (and h) is ”string” too.
Also, the “+” operator is overloaded in js (and in many other programming languages). That means “+”
has more than one meaning in js. As far as our concern is, one meaning is to concatenate two strings and
another meaning is to add two numbers. Because w and h are currently strings “15” and “9”, therefore “+”
concatenates them, and the result is “159”. parseInt() is a function that receives a string as its argument
and returns its equivalent integer number. In other words, it can receive “15” and return 15. It can also
receive “9” and return 9.
In summary, “15”+”9” results in “159”. But, 15+9 results in 24. So, open your ct_Ex1.js file and by using
parseInt, modify the code such that sum of the two inputs are calculated, not their concatenations.
Before going to Exercise 2, compare the code in ct_Ex1.js with your img_01.jpg, i.e., the flowchart you
drew in Exercise 1 of Part 1. Are they conceptually the same? If the answer is “no”, something may be
wrong. Either modify your flowchart to be a good match to this code or provide a js code which is
equivalent to your flowchart. However, note that in the flowchart, we do not go to details of languages.
For instance, we assume “+” means addition as it normally does in real world; but, if in a programming
language “+” has been overloaded, that’s the responsibility of the programmer (not the designer of the
flowchart) to use it properly. As another example, the designer—in their flowchart—does not get involve in
how w and h should be inputted. The designer just states to input w and h. Its the task of the programmer
to translate the flowchart to an appropriate statement in the target programming language, here js;
elsewhere, java, python, c, etc. This is true for many other components in the design. One advantage of
drawing a flowchart first is that you focus on the design, the process of computational thinking, instead of
getting distracted by errands of the programming language, such as how to input, how to convert from
string to number, what the right syntax is, etc. This becomes very critical when you want to tackle bigger
projects.
Exercise 2. Copy ct_Ex1.html and ct_Ex1.js to new files named ct_Ex2.html and ct_Ex2.js.
In this exercise, you should translate your flowchart of Exercise 2 of Part 1 to js. You should make some
changes in both html and js files, such that you get the following results when, for instance, you enter 10,
11, and 4 for the sides of the triangle.
In particular, you need to make about 6 changes in your ct_Ex2.html as follows:
a) Make sure you link your html file to your new js file
b) Change the header to be “area of a triangle when you enter three good sides”
c) Add a new input (because this program receives 3 inputs) with id “num3”
d) Correct the labels of the inputs to a, b, and c
e) As side of a triangle cannot be negative numbers change the min and max to 1 and 100
f) When the “enter” button is clicked, the event handler area() should be triggered.
Also, you need to make about 5 changes in your ct_Ex2.js as follows:
a) Make sure name of the function is area()
b) Make sure pre/post conditions are updated to reflect how this function works
c) Add a line to capture the value of c
d) Replace the line s=w+h; with what you have in your flowchart for Heron’s formula
e) Correct the output to have a more relevant label and correct value as the picture above illustrates
Note that the answer is fixed to 2 digits after the decimal point. This should be addressed in the
implementation, not necessarily the design (i.e., flowchart).
Before moving on to Exercise 3, compare your code in ct_Ex2.js with your img_02.jpg, your flowchart for
this problem. Make sure they are match.
Exercise 3. Copy ct_Ex2.html and ct_Ex2.js to new files named ct_Ex3.html and ct_Ex3.js.
In this exercise, you should translate your flowchart of Exercise 3 of Part 1 to js. You should make some
changes in both html and js files, such that you get the following results when, for instance, you enter -3,
4, and 3 as the coefficients of the quadratic equation.
In particular, you need to make about 4 changes in your ct_Ex3.html as follows:
a) Make sure you link your html file to your new js file
b) Change the header to be “finding roots of a quadratic equation”
c) Change back min and max to -32768 and 32767, respectively
d) When the “enter” button is clicked, the event handler equation() should be triggered.
Also, you need to make about 4 changes in your ct_Ex3.js as follows:
a) Make sure name of the function is equation()
b) Make sure pre/post conditions are updated to reflect how this function works
c) Replace the lines you had for heron’s formula; with what you have in your img_03.jpg
d) Correct the output to have a more relevant label and correct value as the picture above shows
Again, note that the answer is fixed to 2 digits after the decimal point. Also note that roots are shown in
different lines.
Before moving on to Exercise 4, compare your code in ct_Ex3.js with your img_03.jpg, your flowchart for
this problem. Make sure they are match.
Exercise 4. Copy ct_Ex3.html and ct_Ex3.js to new files named ct_Ex4.html and ct_Ex4.js.
In this exercise, you should translate your flowchart of Exercise 4 of Part 1 to js. You should make some
changes in both html and js files, such that you get one of the following results depending on the inputs.
In particular, you need to make 2 changes in your ct_Ex4.html as follows:
a) Make sure you link your html file to your new js file
b) Change the header to be “about roots of a quadratic equation”
Also, you need to make 3 changes in your ct_Ex4.js as follows:
a) Make sure pre/post conditions are updated to reflect how this function works
b) Replace the lines you had for calculating the roots with what you have in your img_04.jpg to
determine if the equation has one, two, or no roots in real numbers
c) Correct the output to reflect the message
Before moving on to Exercise 5, compare your code in ct_Ex4.js with your img_04.jpg, your flowchart for
this problem. Make sure they are match.
Exercise 5. Copy ct_Ex4.html and ct_Ex4.js to new files named ct_Ex5.html and ct_Ex5.js.
In this exercise, you should translate your flowchart of Exercise 5 of Part 1 to js.
In particular, you need to make 3 changes in your ct_Ex5.html as follows:
a) Make sure you link your html file to your new js file
b) Change the header to be “mapping a numerical grade to a letter grade”
c) When the “enter” button is clicked, the event handler mapping() should be triggered.
Also, you need to make 4 changes in your ct_Ex5.js as follows:
a) Make sure name of the function is mapping()
b) Make sure pre/post conditions are updated to reflect how this function works
c) Remove codes from line 9 to the comment above the switch statement
d) Uncomment the block that the switch statement is in
Now, save the changes and launch ct_Ex5.html with your browser. If you enter any number greater than
79, it is correctly mapped to an A or A+; Also, if you enter any number less than 40, it is correctly mapped
to F. But, if you enter, any number between 40 and 79, it’s not mapped correctly. Your task is to fix this
issue.
In particular, you need to make one big change in your ct_Ex5.js as follows: add seven more cases to the
switch statement to map other grades to B+, B, C+, C, D+, D, and E correctly.
Now, compare your code in ct_Ex5.js with your img_05.jpg, your flowchart for this problem. Make sure
they are match. That means if in your flowchart, you used several if statements instead of a switch, you
should change either your js code or your flowchart.
Exercise 6 (further practice):
Only If you have done previous tasks perfectly, you may want to continue this project and add at least two
more flowcharts (from exercises 6-8 of part 1) and corresponding js implementations.
Hint. Even though in the flowcharts of exercises 6-8, you may have while loops, you do not really need
them in js because your code is event-driven: every time the button is clicked, next iteration of the loop is
conducted. Loops will be covered in next lectures.
G. AFTER-LAB WORKS (THIS PART WILL NOT BE GRADED)
In order to review what you have learned in this lab as well as expanding your skills further, we recommend the
following questions and extra practices:
1) You should revisit the 8 exercises after the lab and learn about the parts of your flowcharts that
were not a good match to your js code.
a. You may want to do some sort of reverse engineering here: study the js code that you
eventually developed for each exercise and draw a flowchart for that. Be careful not to
include any JavaScript specific notation in your flowcharts. Flowcharts should be as
independent as possible from programming languages. That means your flowchart should
be understandable to anyone who knows programming even if he/she does not know any
JavaScript.
b. Hence, your flowchart should not use functions like parseFloat, getElementById, etc.,
or keywords like if, else, var, etc. You are also highly discouraged to use “=” for an
assignment; instead you should use “”.
2) Once you have your own 8 flowcharts and corresponding js codes polished, take photos (or
screenshots) of each and add them to your myLearningKit webpage such that when buttons 1 to
8 are clicked, your corresponding solutions are shown.
3) We will provide you with sample solutions on Feb 5. The sample solution should NOT be used as a
means of learning how to tackle those 8 exercises. Instead, it should be only used as a reference to
compare your own solution with our solution and learn from differences. In general, you cannot
learn much computational thinking skills, if any, by studying a solution without putting your efforts
first to come up with a solution (even a non-perfect one). As an analogy, no one can learn how to
ride a bicycle practically by watching (even 100s of hours of) how others do it. This is true for many
other skills including computational thinking.
Please feel free to discuss any of these questions in the course forum or see the TAs and/or Instructors for help.

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