quick assertions for demonstrating JavaScript stuff in jsFiddle, codepen, etc

main.css

p.failed {
  color: red;
}

main.js

function assert(expected, message) {
  var p$ = $('<p></p>');
  if (!expected) {
    p$.addClass('failed');
  }
  p$.text(message);
  p$.appendTo(document.body);
}