A Gentle Introduction to Functional JavaScript: Part 1

addMagicClass.js

function addMagicClass(id) {
    var element = document.getElementById(id);
    element.className += ' magic';
    return element;
}

var unicornEl = addMagicClass('unicorn');
spin(unicornEl);

var fairyEl = addMagicClass('fairy');
sparkle(fairyEl);

var kittenEl = addMagicClass('kitten');
rainbow(kittenEl);