如果你想知道(或等待)直到样式本身加载，这是有效的:

// this will work in IE 10, 11 and Safari/Chrome/Firefox/Edge
// add ES6 poly-fill for the Promise, if needed (or rewrite to use a callback)

let fetchStyle = function(url) {
  return new Promise((resolve, reject) => {
    let link = document.createElement('link');
    link.type = 'text/css';
    link.rel = 'stylesheet';
    link.onload = () => resolve();
    link.onerror = () => reject();
    link.href = url;

    let headScript = document.querySelector('script');
    headScript.parentNode.insertBefore(link, headScript);
  });
};

用法:

fetchStyle(url)
 .then(
   () => console.log("style loaded succesfully"),
   () => console.error("style could not be loaded"),
);

如果你使用jquery:

$('head').append('<link rel="stylesheet" type="text/css" href="style.css">');

使用以下代码:

var element = document.createElement("link");
element.setAttribute("rel", "stylesheet");
element.setAttribute("type", "text/css");
element.setAttribute("href", "external.css");
document.getElementsByTagName("head")[0].appendChild(element);

可以用于这个YUI库，也可以使用本文实现

use:

document.getElementById("of head/body tag")
        .innerHTML += '<link rel="stylesheet" type="text/css" href="style.css">';

var elem = document.createElement('link');
elem.rel = ' stylesheet'
elem.href= 'style.css';//Link of the css file
document.head.appendChild(elem);