Inject jQuery into a page (e.g. via console)

log.js

var s = document.createElement('script');
    s.setAttribute('type', 'text/javascript');
    s.setAttribute('src', 'https://ajax.googleapis.com/ajax/libs/jquery/2.0.2/jquery.min.js');
    
var head = document.getElementsByTagName('head')[0];
if (head) {
  head.appendChild(s);
} else {
  document.body.appendChild(s);
}