Computer Science & Software Engineering

Course Progress 0/0
Week 5 Nested Conditionals

Nested Conditionals

5 min read

Introduction

Picture this: You’re getting ready for school in the morning.

First, you check the weather forecast.

IF it’s raining:

  • You grab your umbrella, But then you need to check another thing - how cold is it?
    • IF it’s also cold, you pack both your umbrella AND your jacket.
    • ELSE (if it’s raining but it’s still warm outside), just the umbrella is enough.

ELSE (if it’s not raining):

  • You skip the umbrella, BUT you still need to check the temperature.
    • IF it’s cold, you’ll take a jacket.
    • ELSE, you’re good to go!

See how you’re making decisions INSIDE other decisions? That’s a nested conditional!

Nested Conditional Code

Now let’s look at an example of the nested conditional code using the analogy above.

// Check the weather before leaving for school
if (raining) {
    // First decision: It's raining, so take umbrella
    takeUmbrella();
    
    // Nested decision INSIDE the raining condition
    if (cold) {
        takeJacket();
        console.log("Taking umbrella AND jacket");
    } else {
        console.log("Taking just umbrella");
    }
    
} else {
    // First decision: Not raining, skip umbrella
    
    // Nested decision INSIDE the not-raining condition
    if (cold) {
        takeJacket();
        console.log("Taking just jacket");
    } else {
        console.log("Nothing needed - good to go!");
    }
}

In the code example above, there are 2 nested conditionals: there’s one in the if statement, and one in the else statement. If it’s raining, the temperature check inside the if block will run. If it’s not raining, we skip the if block entirely and go to the else statement, where a different temperature check will run.

Now you go ahead and try!

%%js

const NUMBERS = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

for (let number of NUMBERS) {
    if (number % 2 === 0) {
        console.log(number + " is even");
        if (number % 3 === 0) {
            console.log(number + " is divisible by 3");
        }
        
        // TODO: Add a nested if statement here to check if divisible by 3
        
    } else {
        console.log(number + " is odd");
        if (number % 3 === 0) {
            console.log(number + " is divisible by 3");
        }
        
        // TODO: Add a nested if statement here to check if divisible by 3
        
    }
}

// Expected output:
// 1 is odd
// 2 is even
// 3 is odd
// 3 is also divisible by 3
// 4 is even
// 5 is odd
// 6 is even
// 6 is also divisible by 3
// 7 is odd
// 8 is even
// 9 is odd
// 9 is also divisible by 3
// 10 is even

Code Runner Challenge

Now, you're a bouncer at a nightclub. You need to make a for loop with a nested conditional that will check if people are of the correct age, and if they aren't, it should check if they wear sunglasses. If they are underage but they still have sunglasses, they should be let in.

View IPYNB Source 
%%js

// CODE_RUNNER: Now, you're a bouncer at a nightclub. You need to make a for loop with a nested conditional that will check if people are of the correct age, and if they aren't, it should check if they wear sunglasses. If they are underage but they still have sunglasses, they should be let in.

// List of people trying to get into the nightclub
const people = [
  { name: 'jimmy', age: 15, wearsSunglasses: false },
  { name: 'sara', age: 5, wearsSunglasses: true },
  { name: 'alex', age: 22, wearsSunglasses: true },
  { name: 'morgan', age: 18, wearsSunglasses: false },
  { name: 'dakota', age: 21, wearsSunglasses: false },
  { name: 'casey', age: 25, wearsSunglasses: true }
];

// Check everyone at the door
for (const person of people) {
  if (person.age >= 21) {
      if (person.wearsSunglasses === true) {
          console.log(person + " is free to enter because they're over 21 and they have sunglasses");
      } else {
              console.log(person + " is free to enter");
      }
                      
    // TODO: Add nested conditional to check if person wears sunglasses
    // If they do, print: person.name + " is free to enter because they're over 21 and they have sunglasses"
    // Otherwise, print: person.name + " is free to enter"

  } else {
      if (person.wearsSunglasses === true) {
          console.log(person + " is free to enter because they have sunglasses");
  } else {
      console.log(person + " is not free to enter because they are underage");
  }
    
      
    // TODO: Add nested conditional to check if person wears sunglasses
    // If they do, print: person.name + " is free to enter because they have sunglasses"
    // Otherwise, print: person.name + " is not free to enter because they are underage"

  }
}
Lines: 1 Characters: 0
Output
Click "Run" in code control panel to see output ...

Homework

Make a nested conditional that does the following:

  1. contains more than 1 nested conditional
  2. use the numbers 1-50
  3. check if each number is divisible by each factor of 50

Code Runner Challenge

Make a nested conditional homework

View IPYNB Source 
%%js

// CODE_RUNNER: Make a nested conditional homework
const NUMBERS = [
  1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
  11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
  21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
  31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
  41, 42, 43, 44, 45, 46, 47, 48, 49, 50
];

for (let number of NUMBERS) {

  if (number % 2 === 0) {
    console.log(number + " is divisible by 2");

    if (number % 5 === 0) {
      console.log(number + " is divisible by 5");

      if (number % 10 === 0) {
        console.log(number + " is divisible by 10");

        if (number % 25 === 0) {
          console.log(number + " is divisible by 25");

          if (number % 50 === 0) {
            console.log(number + " is divisible by 50");
          }
        }
      }
    }
  } else {
    console.log(number + " is not divisible by a factor of 10");
  }
}
Lines: 1 Characters: 0
Output
Click "Run" in code control panel to see output ...

Course Timeline