使用带回调的JavaScript动态加载CSS文件而不使用jQuery

Question

我正在尝试使用javascript动态加载css文件，并且不能使用任何其他js库（例如jQuery）。

css文件已加载，但我似乎无法获得回调来工作。下面是我正在使用的代码

var callbackFunc = function(){
    console.log('file loaded');     
};
var head = document.getElementsByTagName( "head" )[0];
var fileref=document.createElement("link");
    fileref.setAttribute("rel", "stylesheet");
    fileref.setAttribute("type", "text/css");
    fileref.setAttribute("href", url);

    fileref.onload  = callbackFunc;
    head.insertBefore( fileref, head.firstChild );

使用以下代码添加脚本标签以加载js文件可以正常工作并触发回调：

var callbackFunc = function(){
    console.log('file loaded');     
};

var script = document.createElement("script");

script.setAttribute("src",url);
script.setAttribute("type","text/javascript");

script.onload  = callbackFunc ;

head.insertBefore( script, head.firstChild );

我在这里做错什么了吗？还有其他方法可以帮助我实现这一目标吗？

Answer 1

不幸的是，大多数现代浏览器都不支持样式表的加载。我发现有一点谷歌搜索解决方案。

基础

最基本的实现可以通过大约30行（独立于框架）JavaScript代码完成：

function loadStyleSheet( path, fn, scope ) {
   var head = document.getElementsByTagName( 'head' )[0], // reference to document.head for appending/ removing link nodes
       link = document.createElement( 'link' );           // create the link node
   link.setAttribute( 'href', path );
   link.setAttribute( 'rel', 'stylesheet' );
   link.setAttribute( 'type', 'text/css' );

   var sheet, cssRules;
// get the correct properties to check for depending on the browser
   if ( 'sheet' in link ) {
      sheet = 'sheet'; cssRules = 'cssRules';
   }
   else {
      sheet = 'styleSheet'; cssRules = 'rules';
   }

   var interval_id = setInterval( function() {                     // start checking whether the style sheet has successfully loaded
          try {
             if ( link[sheet] && link[sheet][cssRules].length ) { // SUCCESS! our style sheet has loaded
                clearInterval( interval_id );                      // clear the counters
                clearTimeout( timeout_id );
                fn.call( scope || window, true, link );           // fire the callback with success == true
             }
          } catch( e ) {} finally {}
       }, 10 ),                                                   // how often to check if the stylesheet is loaded
       timeout_id = setTimeout( function() {       // start counting down till fail
          clearInterval( interval_id );             // clear the counters
          clearTimeout( timeout_id );
          head.removeChild( link );                // since the style sheet didn't load, remove the link node from the DOM
          fn.call( scope || window, false, link ); // fire the callback with success == false
       }, 15000 );                                 // how long to wait before failing

   head.appendChild( link );  // insert the link node into the DOM and start loading the style sheet

   return link; // return the link node;
}

这将允许您使用如下的onload回调函数加载样式表：

loadStyleSheet( '/path/to/my/stylesheet.css', function( success, link ) {
   if ( success ) {
      // code to execute if the style sheet was loaded successfully
   }
   else {
      // code to execute if the style sheet failed to successfully
   }
} );

或者，如果您希望回调保持其范围/上下文，则可以执行以下操作：

loadStyleSheet( '/path/to/my/stylesheet.css', this.onComplete, this );