动态引入脚本和样式
function loadScript(url) {
var script = document.createElement("script");
script.type = "text/javascript";
script.src=url;
document.body.appendChild(script);
}
function loadStyles(url) {
var link = document.createElement("link");
link.rel="stylesheet";
link.type="text/css";
link.href=url;
var head = document.getElementsByTagName("head")[0];
head.appendChild(link);
}