Switch statements

• The final type of conditional statement is the switch statement.
• Switch statements are used to “switch” among a number of conditions called cases, instead of including tons of else if statements.
• The cases compare the value of the tested variable/value to the value attributed to the case.
• Once the correct value is found, the code in that case is executed.

• If no cases match the tested value, the switch statement executes the “default case”

• Our first switch statement will test different conditions to see what day of the week it is today.

• The switch statement will do this by utilizing a JavaScript date object, which will be covered in a later segment.

• The variables ‘today’ and ‘day’ get the current date from the JavaScript Date object. Objects are covered in a later segment. The value of the day is returned to us in a numeric format, with 0 representing Sunday, 1 representing Monday, and so on.

• We use a switch statement instead of seven if, else if, else statements to determine what day it is.

• The variable day is compared to the values of each case. When the value is matched, the day is printed.

• We always include a default statement in switch statements in case of an error on our part, or in case none of the cases evaluate as true.

• The default case also helps with troubleshooting instead of not having any output when something goes wrong.

See the Pen 3.2 Example by LSU DDEM (@lsuddem) on CodePen.

• Make sure to add a break statement before testing a new case!
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• We can also program switch statements that check more complex conditions
• To do so, we set the variable the switch statement is checking to “true”.
• Now, we can set the conditions for the cases to more complex conditions, such as the cases below:

• This switch example determines the letter grade of a test score out of 100

  let testScore = 73;
  // Note that we use 'true' in place of the tested variable, and incorporate the testScore variable in the case conditions
  switch(true){
  case testScore >= 90:
      console.log(testScore +" / 100 : A");
      break;
  case testScore >= 80:
      console.log(testScore +" / 100 : B");
      break;
  case testScore >= 70:
      console.log(testScore +" / 100 : C");
      break;
  case testScore >= 60:
      console.log(testScore +" / 100 : D");
      break;
  case testScore >= 50:
      console.log(testScore +" / 100 : F");
      break;
  default:
      console.log("Score is too low to even have a grade");
  }
  

Exercise 3.2

See the Pen Exercise 3.2 by LSU DDEM (@lsuddem) on CodePen.