Switch Statements

original slides

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

slides

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!
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.