booleans-conditionals.md

Booleans, Comparisons & Conditionals

Lesson

Slides

Exercises

Basic Requirements

Comparison Operators

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

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

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.