design.md

Design

Learning objectives

• What does a while loop do
• What is the difference to do-while
• Syntax while(){} and do{} while()
• Break and continue
• What is the switch statement
• Syntax switch(){}
• What is the default case for
• What does break do
• Why is break so important when using switch

Out of Scope

The following topics are out of scope because they are covered by another concept exercise.

• For loops
• Array loops (for...in, forEach, map)

Concepts

The Concepts this exercise unlocks are:

• while-loops
• conditionals-switch

Prerequisites

• comparison for writing the condition in the loop header
• conditionals because they introduced the student to the concept of conditional execution
• arrays because they are used to loop over them in the exercise

Analyzer

This exercise could benefit from the following rules in the analyzer. The comment types mentioned below only serve as a proposal.

1. timeToMixJuice

   • essential: Verify the student used a switch statement. Would be nice if we could give different feedback depending on what the student used instead. If it was if-else, comment that switch is better suited for so many different variants. If an object was used, comment that this is nice but the goal is to practice switch.
   • essential: Verify that there are 5 cases and a default case in the switch statement to make sure the student did not tailor their code for the test cases (e.g., used more cases instead of default).
   • actionable: If the student used break, comment to use early returns instead to avoid assigning to a helper variable first and then returning that variable.
   • celebratory: Comment something nice when a student used grouped case statements.

     case 'Energizer':
     case 'Green Garden':
        return 1.5;

2. limesToCut

   • A solution that uses if (limes.length < 0) break; instead of combining the conditions should be considered equally correct to the exemplar solution. The version in the exemplar file is shorter but the break version emphasizes that there is a special edge case.
   • essential: Verify that while was used.
   • essential: If a helper function was used for the switch statement, check that is was not exported.
   • actionable: If the student wrote if (limes.length < 0) return limesCut, comment that the duplication of return limesCut can be avoided by using break there instead of return.
   • actionable: Tell the student to use a helper function to wrap the switch statement for readability if he/she did not do that.
   • informative: If the student used a counter to iterate over the array, show a comment about about shift.
   • informative: Remind the student about ++ if it was not used to increment the lime counter.
   • informative: Check whether a shorthand assignment += was used to increase the loop counter.
   • informative: If default was included in the switch statement, remind the student that it is optional and not needed in the scope of the task.
   • celebratory: Make a positive remark if the student used a helper function to wrap the switch statement.
   • celebratory: Celebrate if the student used ++ and +=.

3. remainingOrders

   • essential: Verify that do-while was used. If while was used instead, say that do-while is a better fit because there is always at least one iteration (because timeLeft is always > 0) and the condition can best be checked after running the code.
   • essential: Verify timeToMixJuice was reused instead of duplicating the code.
   • Most of the points from task 2 also apply here. Check what can be reused.

Notes

The exercise is inspired by the Master Mixologist Exercise in the Swift track. The original exercise also included for loops which is covered by a different exercise in the JavaScript track. The tasks were adapted accordingly which also simplified them. The alcohol was replaced and the name was changed to match the new story.

Improvement

The exercise would benefit from another task to practice continue.