1、创建link标签加载CSS文件

function loadCSS(cssFile) {var link = document.createElement("link");link.rel = "stylesheet";link.type = "text/css";link.href = cssFile;document.head.appendChild(link);
}
// 异步加载CSS文件
loadCSS('path/to/your.css');

2、动态创建<style>标签，将CSS代码插入到文档中

function loadCSSCode(cssCode) {var style = document.createElement('style');style.type = 'text/css';if (style.styleSheet) {// This is required for IE8 and below.style.styleSheet.cssText = cssCode;} else {style.appendChild(document.createTextNode(cssCode));}document.getElementsByTagName("head")[0].appendChild(style);
}
// 动态加载CSS代码
loadCSSCode('.classname { color: red; }');

3、利用import（vue中）

 import('./path/to/your.css').then(css => css.default);