js 添加css或者链接文件

//动态添加css style
var comAddCSS = function (cssText) {
    var style = document.createElement('style'),  //创建一个style元素
        head = document.head || document.getElementsByTagName('head')[0]; //获取head元素
    style.type = 'text/css'; //这里必须显示设置style元素的type属性为text/css，否则在ie中不起作用
    if (style.styleSheet) { //IE
        var func = function () {
            try { //防止IE中stylesheet数量超过限制而发生错误
                style.styleSheet.cssText = cssText;
            } catch (e) {

            }
        }
        //如果当前styleSheet还不能用，则放到异步中则行
        if (style.styleSheet.disabled) {
            setTimeout(func, 10);
        } else {
            func();
        }
    } else { //w3c
        //w3c浏览器中只要创建文本节点插入到style元素中就行了
        var textNode = document.createTextNode(cssText);
        style.appendChild(textNode);
    }
    head.appendChild(style); //把创建的style元素插入到head中
}

function loadScript(url, callback) {
    var script = document.createElement("script")
    script.type = "text/javascript";
    if (script.readyState) { //IE
        script.onreadystatechange = function () {
            if (script.readyState == "loaded" || script.readyState == "complete") {
                script.onreadystatechange = null;
                callback();
            }
        };
    } else { //Others
        script.onload = function () {
            callback();
        };
    }
    script.src = url;
    var head = document.head || document.getElementsByTagName('head')[0];
    head.appendChild(script);
}