Objects and Arrays form the basis of pretty much all data structures in JavaScript and allow us to represent the state of the world to be manipulated. This exercise is all about how to represent objects in the real world in an 'IT' way. By thinking about the data structure you can make it easier to implement certain functionality which will help code stay simple and readable!

In the traffic-light-1.js and traffic-light-2.js files we give two different ways of representing a traffic light. Have a look at the files and think about the following:

• In the first version we create an object with a state property. Why do you think we do this? Why not just a variable?
• In the second version we add extra information (the possibleStates property). What do you think the advantage is of that?
• In the second version the stateIndex property is a number, why do you think that is?

In the hyf.js file we have a more complex representation of the hyf program. We have divided the hyf world into 4 what we call entities: modules, classes, students, mentors. The export statements are for week 4, you can ignore those for now! Have a look and think about the following:

• Why do you think we have a name and displayName property for the modules?
• Do you think active and start/graduationDate are both needed in the classes array? Why or why not?

Next to the questions specific to each representation, also have a think about the following:

• In all of the examples, you will see that objects and arrays are mostly defined using a const statement rather than a let even if we change the value of the object or array, why do you think this is the case?