• Revisit abstraction

Before we jump into more code, let's think for a moment about something you encounter pretty much every day when you read a news article or email: the way we organize words to express and clarify meaning. For example, a paragraph is a collection of sentences, introduced by a topic sentence and bundled up or closed by a closing sentence. A paragraph can persuade or offend, direct or explain. A paragraph has a function.

"Code paragraphs" are called, depending on language, "functions," "procedures," "methods," or "subroutines." They bundle up expressions and statements to accomplish a task. Just as "Make a Sandwich" encompasses specific, "atomic" actions like "get slice of bread," "get jelly," etc., executeTransfer encompasses logic like if (accountStatus === "open") or if (accountBalance >= transactionAmount).

To have code that is easy to read, debug, and maintain, we need to bundle collections of atomic activities into "code paragraphs" that do work. JavaScript calls these "functions."

This process of bundling up small atoms into a function is called "abstraction." "Abstraction" comes from the Latin word for "to pull away." When we're further away, many details are hard to see. Only the most relevant shapes are recognizable. For example, when you're on an airplane overlooking a city, the details of the cars below — the mileage, what's in the cup holder, the make or model — are invisible; they're not essential. But what we may be able to see is the vehicle type (car vs. truck) or the color of the car. By abstracting we see what's true at a higher level, or more generally.

Here are a few more "abstractions:"

• Jerry Seinfeld, Ruth Bader Ginsburg, and Cardi B are atomic individuals, but we can refer to them all collectively by the abstraction (or they can be abstracted into) "famous New Yorkers"
• Books about a killer dog, a scary alter ego, and a scary clown can be abstracted into the name "horror novels (by Stephen King)"
• Individuals with strange powers and (usually) strange clothing can be abstracted into "superheroes"

Abstraction is a natural part of learning to converse. When you're first learning to communicate, you don't know enough to start talking about abstractions. You prefer to think about real, visible, tangible things. But as you learn about opposites, how things are similar (and how perhaps one thing is dissimilar) you grow in your ability to abstract.

In fact, the thing that makes most higher learning "higher" is that the discussion, work, and discovery is focused on uncovering general principles that allow us to predict how things will work more-or-less most of the time. Amazingly, this was considered a pretty revolutionary idea at the time when Galileo and Newton started doing it. The moment that natural philosophers started looking for these "general rules of how things work," science as we know it was born.

In Programming as Conversation 3, we'll learn to take our JavaScript expressions and statements and bundle them up into abstractions called functions. Before we get to that, however, we first need to learn a little about testing in JavaScript.