Exercises: Booleans and Conditionals

Attempt these exercises to test your understanding. Don’t worry if you struggle while working on them. Struggling and then reviewing the material will help you remember it.

Take note of any problem here or topic from this chapter that you don’t understand. Take a break and return to the problem. Do you see it in a new way or have a better understanding? If not, try spending five minutes researching the topic. Start with this book and if you still have questions, ask one on the internet or Slack/Discourse. You’re not the first person to learn to code and you’re definitely not the first person to ask a question or get stuck!

1. Declare and initialize the following variables for our space shuttle

let engineIndicatorLight = "red blinking";
let spaceSuitsOn = true;
let shuttleCabinReady = true;
let crewStatus = spaceSuitsOn && shuttleCabinReady;
let computerStatusCode = 200;
let shuttleSpeed = 15000;

2. Examine the code below. What will be printed to the console?

   Use the value of engineIndicatorLight defined above to answer this question.

   if (engineIndicatorLight === "green") {
      console.log("engines have started");
   } else if (engineIndicatorLight === "green blinking") {
      console.log("engines are preparing to start");
   } else {
      console.log("engines are off");
   }

3. Write conditional expressions to satisfy the safety rules.

   Use the variables defined from the table above to satisfy the rules listed below.

• crewStatus

  • If the value is true, print “Crew Ready”
  • Else print “Crew Not Ready”
  Check Your Solution

  if (crewStatus) {
    console.log("Crew Ready");
  } else {
    console.log("Crew Not Ready");
  }

• computerStatusCode

  • If the value is 200, print “Please stand by. Computer is rebooting.”
  • Else if the value is 400, print “Success! Computer online.”
  • Else print “ALERT: Computer offline!”
  Check Your Solution

  if (computerStatusCode === 200) {
    console.log("Please stand by. Computer is rebooting.");
  } else if (computerStatusCode === 400) {
    console.log("Success! Computer online.");
  } else {
    console.log("ALERT: Computer offline!");
  }

• shuttleSpeed

  • If the value is > 17500, print “ALERT: Escape velocity reached!”
  • Else if the value is < 8000, print “ALERT: Cannot maintain orbit!”
  • Else print “Stable speed”
  Check Your Solution

  if (shuttleSpeed > 17500) {
    console.log("ALERT: Escape velocity reached!");
  } else if (shuttleSpeed < 8000) {
    console.log("ALERT: Cannot maintain orbit!");
  } else {
    console.log("Stable speed.");
  }

4. PREDICT

   Do these code blocks produce the same result? Answer Yes or No.

   if (crewStatus && computerStatusCode === 200 && spaceSuitsOn) {
      console.log("all systems go");
   } else {
      console.log("WARNING. Not ready");
   }

   if (!crewStatus || computerStatusCode !== 200 || !spaceSuitsOn) {
      console.log("WARNING. Not ready");
   } else {
      console.log("all systems go");
   }

5. Monitor the shuttle’s fuel status.

   Implement the checks below using if / else if / else statements. Order is important when working with conditionals, and the checks below are NOT written in the correct sequence. Please read ALL of the checks before coding and then decide on the best order for the conditionals.

• If fuelLevel is above 20000 AND engineTemperature is at or below 2500, print “Full tank. Engines good.”
• If fuelLevel is above 10000 AND engineTemperature is at or below 2500, print “Fuel level above 50%. Engines good.”
• If fuelLevel is above 5000 AND engineTemperature is at or below 2500, print “Fuel level above 25%. Engines good.”
• If fuelLevel is at or below 5000 OR engineTemperature is above 2500, print “Check fuel level. Engines running hot.”
• If fuelLevel is below 1000 OR engineTemperature is above 3500 OR engineIndicatorLight is red blinking, print “ENGINE FAILURE IMMINENT!”
• Otherwise, print “Fuel and engine status pending…”

if (fuelLevel < 1000 || engineTemperature > 3500 || engineIndicatorLight === "red blinking"){
  console.log("ENGINE FAILURE IMMINENT!");
} else if (fuelLevel <= 5000 || engineTemperature > 2500){
  console.log("Check fuel level. Engines running hot.");
} else if (fuelLevel > 20000 && engineTemperature <= 2500){
  console.log("Full tank. Engines good.");
} else if (fuelLevel > 10000 && engineTemperature <= 2500){
  console.log("Fuel level above 50%. Engines good.");
} else if (fuelLevel > 5000 && engineTemperature <= 2500){
  console.log("Fuel level above 25%. Engines good.");
} else {
  console.log("Fuel and engine status pending...");
}

6. Final bit of fun!

   The shuttle should only launch if the fuel tank is full and the engine check is OK. However, let’s establish an override command to ignore any warnings and send the shuttle into space anyway!

• Create the variable commandOverride, and set it to be true or false.

  If commandOverride is false, then the shuttle should only launch if the fuel and engine check are OK.

  If commandOverride is true, then the shuttle will launch regardless of the fuel and engine status.

• Code the following if / else check:

  If fuelLevel is above 20000 AND engineIndicatorLight is NOT red blinking OR commandOverride is true print “Cleared to launch!”

  Else print “Launch scrubbed!”