Forged-Workshop-2

Comparison Operators

Basic Practice (5 points each)

1. Type the two boolean values -- true and false -- into your console.

2. Use the console to accomplish the following:

   • Write an expression using > that will evaluate to false
   • Write an expression using > that will evaluate to true
   • Write an expression using < that will evaluate to false
   • Write an expression using < that will evaluate to true
   • Write an expression using two numbers and === that will evaluate to true
   • Write an expression using two numbers and === that will evaluate to false
   • Write an expression using two strings and === that will evaluate to true
   • Write an expression using two strings and === that will evaluate to false

3. Fill in the ??? with the following operators or values to make the statements output the expected Boolean value.

   12 ??? 78
   // => true
   
   24 ??? 16
   // => false
   
   45 !== ???
   // => true
   
   "45" ??? 45
   // => false
   
   "6" ??? "six"
   // => true

4. Write a function oldEnoughToDrink that takes an age as an argument and returns true if the person with that age is old enough to drink.

5. There's an easy way to figure out how long a string is by adding .length to the end of it. Try this out in the console:

"hello".length;
"".length;
"John Doe".length;

Write a function sameLength that accepts two strings as arguments, and returns true if those strings have the same length, and false otherwise.

6. Write a function passwordLongEnough that accepts a "password" as a parameter and returns true if that password is long enough -- you get to decide what constitutes long enough.

Conditionals: if

Basic Practice (5 points each)

1. Write a function bouncer that accepts a person's name and age as arguments, and returns either "Go home, NAME.", or "Welcome, NAME!" (where NAME is the parameter that represents the person's name) depending on whether or not the person is old enough to drink.

2. Write a function max that takes two numbers as arguments, and returns the larger one.

3. Write a function min that takes two numbers as arguments, and returns the smaller one.

4. Write functions larger and smaller that each accept two strings as arguments, and return the larger and smaller strings, respectively.

More Practice (10 points each)

1. Fill in the ??? with the following operators or values to make the statements output the expected Boolean value.

   106 ??? 12
   // => false
   
   "wiz" ??? "wiz"
   // => true
   
   7 * 7  ??? 49
   // => true
   
   12 ??? (24 / 2)
   // => false
   
   (20 % 2) <= ???
   // => true
   
   (9 / 3) + (5 * 5) === ???
   // => true

2. Write the following functions that each accept a single number as an argument:

   • even: returns true if its argument is even, and false otherwise.
   • odd: the opposite of the above.
   • positive: returns true if its argument is positive, and false otherwise.
   • negative: the opposite of the above.

3. A couple of other useful built-in mathematical functions are Math.random, Math.floor and Math.ceil. Look these functions up on MDN to learn how they work, and use them to implement the following functions:

   • randInt: Should accept a single numeric argument (n), and return a number from 0 to n.

   • guessMyNumber: Should accept a single numeric argument and compare it to a random number between 0 and 5. It should return one of the following strings:

     • "You guessed my number!" if the argument matches the random number.
     • "Nope! That wasn't it!" if the argument did not match the random number.

Logical Operators

Basic Practice (5 points each)

1. Is the ! operator a unary operator, or binary operator?

2. Evaluate each of the following expressions first on a whiteboard, and then in a console:

   !(2 >= 2)
   !(4 === 4)
   !(5 !== 5)

3. Evaluate each of the following expressions first on a whiteboard, and then in a console:

   1 > 2 || 2 > 2 || 3 > 2
   5 < 5 || 75 < 74

Conditionals: else if & else

Basic Practice (5 points each)

1. This guy named "Joe" keeps blacking out at the bar that your function, bouncer (from the previous module), is in charge of; thus, management has decided to add him to the "blacklist" -- modify the bouncer function from the previous section so that the person named "Joe" is rejected with an appropriate message, regardless of his age.

2. Write a function called scoreToGrade that accepts a number as a parameter and returns a string representing a letter grade corresponding to that score.

   For example, the following grades should be returned given these scores:

   • 'A' >= 90
   • 'B' >= 80
   • 'C' >= 70
   • 'D' >= 60
   • 'F' < 60

   function scoreToGrade(score) {
     // TODO: your code here
   }
   scoreToGrade(95); // => 'A'
   scoreToGrade(72); // => 'C'

3. Modify the scoreToGrade function so that it returns 'INVALID SCORE' if the score is greater than 100 or less than 0.

More Practice (10 points each)

1. Think of at least three activities that you enjoy doing outdoors and the range of temperatures and weather patterns (e.g sunny, windy, snowy, rainy, etc.) that are best for these activities. Write a function whatToDoOutside that accepts a temperature and condition as parameters and outputs a string of the format: "The weather is ideal for: ACTIVITY" (where ACTIVITY is an actual activity). Make sure to include an else that indicates what should be done if the conditions do not match any activities. If you're short on inspiration, here are some ideas:

   • Snow Sports: snowboarding, skiing
   • Water Sports: surfing, sailing, paddle boarding, swimming
   • Team Sports: basketball, baseball, football (American or everywhere else), etc.

2. The guessMyNumber function from the Booleans & Conditionals module (More Practice section) accepts a guess n and checks it against a random number from 0 to 5 -- if the guess n is greater than 5, output a different message indicating that the guess is out of bounds.

   • NOTE: It will be helpful to first write a randInt function that accepts a number n and computes a random integer from 0 to n; then, you can use this function in guessMyNumber.

3. Modify the scoreToGrade function so that it returns 'A+/A-' for scores of 98-100/90-92 respectively. Apply the same logic for all other letter grades.

Advanced (15 points each)

1. The bar that employs our bouncer function has decided to do live music on Friday and Saturday nights, and will be admitting those that are over 18 to the bar on those nights; the catch however, is that all who are 21 or older will need to be given a wristband to distinguish them from the minors. Modify your bouncer function to handle this situation.

2. You should have noticed a large amount of repetitive code when modifying scoreToGrade to accommodate + or - grades. When we do lots of repetitive things, that's a clear signal that there's a better way. Write a helper function letterGrade that accepts two arguments, letter and score, and works as follows:

   function letterGrade(letter, score) {
     // your code here
   }
   // These are examples of what a *working* function would output.
   letterGrade('A', 95); // => 'A'
   letterGrade('A', 91); // => 'A-'
   letterGrade('B', 88); // => 'B+'
   letterGrade('monkey', 160); // => 'monkey-'

   Finally, use letterGrade to remove the repetition in scoreToGrade.

3. It turns out that we can write logical and and logical or in terms of each other and logical not using De Morgan's Laws.

   • Write a function or that works like ||, but only uses ! and &&.
   • Write a function and that works like &&, but only uses ! and ||.

Variables

Basic Practice (5 points each)

1. Fix each of the following variable declarations in a console -- some are syntactically invalid, some are disobey style guidelines, and some are just weird.

   var "animal" = "monkey";
   var "monkey" = animal;
   var x= 15;
   var y =10;
   var var = "huh?";
   var true = false;
   var isTenEven = 10 % 2 = 0;

2. Perform the following in the console:

   • Create a variable firstName and assign your first name to it.
   • Create another variable, lastName, and assign your last name to it.
   • Have a middle name? If so, repeat the process.
   • Now, create a variable fullName and assign your full name to it by using the above variables.

3. For each of the following code blocks, use a whiteboard (or a piece of paper) to reason about what the value of x is supposed to be on the last line. Once you have arrived at a conclusion that you are comfortable with, enter the lines into a console and check your answer. Was your hypothesis correct? If not, ensure that you understand why (talk with a classmate, or ask for help).

   var x = 5;
   x + 10;
   x; // => ???

   var x = 17;
   x = (x + 1) / 2;
   x * 4;
   x; // => ???

   var x = 5;
   var y = 20;
   x = y;
   y = y + 7;
   x; // => ???

   var x = 10;
   var y = 5;
   x = (x * 4) - 3;
   x + 17;
   x = x + y;
   x; // => ???

4. Write a function called counter that, when invoked, always returns a number that is one more than the previous invocation. For instance:

   function counter() {
     // TODO: your code here
   }
   counter(); // => 1
   counter(); // => 2
   counter(); // => 3
   // etc.

   HINT: You'll need a variable for this. Where should the variable be declared?