手写jsonp

为什么有时候jquery的ajax会不好使呢？试试自己的jsonp吧

function jsonp(src) {
  var script = document.createElement('script'),
      s = document.getElementsByTagName('script')[0];

  script.onreadystatechange = script.onload = function () {
    if (!script.readyState || /loaded|complete/i.test(script.readyState)) {
      script.onreadystatechange = script.onload = null;
      script.parentNode.removeChild(script);
    }
  };

  script.type = 'text/javascript';
  s.parentNode.insertBefore(script, s);
  script.src = src;
}

jsonp(src + '&callback=aaaaa');