Functions

Functions are reusable blocks of code. They follow the DRY principle — Don't Repeat Yourself.

Function Declaration

function greet(name) {
  return 'Hello, ' + name + '!'
}
console.log(greet('Alice')) // Hello, Alice!

Function Expression

const greet = function(name) {
  return 'Hello, ' + name + '!'
}
console.log(greet('Bob')) // Hello, Bob!

Arrow Function

const greet = (name) => 'Hello, ' + name + '!'

// Shorter version (one parameter, one expression):
const greet = name => \`Hello, \${name}!\`

console.log(greet('Carol')) // Hello, Carol!

Naming Conventions

Use action verbs to name functions. Common prefixes:

• get — return a value: getUserName()
• calc — calculate: calcTotal()
• create — create something: createUser()
• check — return boolean: checkIsAdmin()

Parameters vs Arguments

// 'name' is a parameter (in definition)
function greet(name) {
  return \`Hello, \${name}!\`
}

// 'Alice' is an argument (in call)
greet('Alice')