Chapter 07 — Functions

Level: beginner Estimated time: 6 h Prerequisites: chapter 06 — Collections: List, Set, and Map What you will be able to do by the end: break a program into clear functions with parameters, return values, optional and named parameters, and write a small combat engine built entirely from functions.

07.0 — Chapter objectives

By the end of this chapter, you will be able to:

• understand why a function prevents code repetition;
• declare a function;
• call a function;
• understand the void keyword;
• return a value with return;
• choose a return type;
• define parameters;
• pass arguments;
• use multiple parameters;
• distinguish positional parameters from named parameters;
• use optional [ ] parameters;
• use named { } parameters;
• use required;
• provide default values;
• write arrow functions =>;
• write anonymous functions;
• understand variable scope;
• distinguish local variables from global variables;
• pass a function as a parameter to another function;
• write a simple recursive function;
• break a large program into small functions.