Eloquent JavaScript, 2nd Edition

Chapter 3. Functions

“People think that computer science is the art of geniuses but the actual reality is the opposite, just many people doing things that build on each other, like a wall of mini stones.”

—Donald Knuth

You’ve seen function values, such as alert, and how to call them. Functions are the bread and butter of JavaScript programming. The concept of wrapping a piece of program in a value has many uses. It is a tool to structure larger programs, to reduce repetition, to associate names with subprograms, and to isolate these subprograms from each other.

The most obvious application of functions is defining new vocabulary. Creating new words in regular, human-language prose is usually bad style. But in programming, it is indispensable. ...