What are JavaScript functions?

JavaScript functions can be defined in several ways:

1. Function Declaration:

function greet(name) {
  return "Hello " + name;
}

2. Function Expression:

const greet = function(name) {
  return "Hello " + name;
};

3. Arrow Function (ES6):

const greet = (name) => {
  return "Hello " + name;
};
// Or shorter:
const greet = name => "Hello " + name;

4. Constructor Function:

const greet = new Function("name", "return 'Hello ' + name");

Functions are first-class objects in JavaScript, meaning they can be assigned to variables, passed as arguments, and returned from other functions.