JavaScript Functions as First Class Data: Array of Functions

Learning Goals

- Create a JavaScript function that loops through a function Array

Introduction

Since functions in JavaScript are "first-class" objects, it means they can be
treated like any other data type in JavaScript (Number, String, et al.). A
fun way to experience this truth is to load up an Array of Functions and
then call each Function.

$3

Let's create an Array of dog-care functions so that we can report on the
activities we take in caring for Byron the Poodle.

When this program runs, it should print out:

``
console.log("Wake Byron the poodle");
console.log("Leash Byron the poodle");
console.log("Walk to the park with Byron the poodle");
console.log("Throw the frisbee for Byron the poodle");
console.log("Walk home with Byron the poodle");
console.log("Unleash Byron the poodle");
`

Start by creating a function for every activity that you see listed above:

For example:

`js
function wakeDog() {
console.log("Wake Byron the poodle");
}
...
`

But wait, if we write it in this way, all of our uses of this function will be
for Byron the poodle. Let's _generalize_ now and make each function take a
dogName and dogBreed parameter. Thus:

`js
function wakeDog(dogName, dogBreed) {
console.log(Wake ${dogName} the ${dogBreed});
}
...
`

Additionally: Each function should return the string that it creates. That
is, we should create a String, log it to the console (using console.log()), and return that String.

Create the Array o' Functions

Continue writing _"generalized"_ functions for

* wakeDog
* leashDog
* walkToPark
* throwFrisbee
* walkHome
* unleashDog

Each function's implementation will be a generalized invocation of
console.log().

Create the Array o' Functions

Next, create our "Array o' Functions!" Create a variable called routine. This
variable will be an Array all of the functions we've just defined.

Create a Function to Process the Array o' Functions

Lastly, create the function called exerciseDog that will take in two
arguments:

* dogName
* dogBreed

The function's implementation should

* Iterate over the routine Array
* Call each function in the array and
* pass the dogName and dogBreed received by exerciseDog() to the function as they are _called_
* capture the result of each function's call
* return an Array of all those functions' return values

Conclusion

This lab demonstrates the power of Functions as first-class data. We can
stack them up in Arrays or assign them inside of Objects or save them to
variables, or iterate over them. Instead of _merely_ having Arrays of
String`s and other familiar items, we can stuff them with _work_. And that's
nothing short of amazing!

First Class Functions MDN