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Great job! By thinking about functions as data, and learning about higher-order functions, you’ve taken important steps in learning to write clean, modular code that takes advantage of JavaScript’s flexibility.

Let’s review what we learned in this lesson:

  • Abstraction allows us to write complicated code in a way that’s easy to reuse, debug, and understand for human readers.

  • We can work with functions the same way we work with any other type of data, including reassigning them to new variables.

  • JavaScript functions are first-class objects, so they have properties and methods like any other object.

  • Functions can be passed into other functions as parameters.

  • A higher-order function is a function that either accepts functions as parameters, returns a function, or both.


Feel free to play around with the code in the workspace.

  • What happens if you change the value of 2 in checkA?
  • Which variable holds the callback function?
  • What happens if you invoke the function’s argument?

In the following lesson, you’ll learn how higher-order functions are used in some of the most important and widely-used JavaScript methods, iterators!

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