jQuery 相当于 PHP 的 file_exists()？

Question

在下面的代码片段中，从我的 jQuery 设置中，我需要检查图像文件是否确实存在，如果不存在，我想替换默认图像。目前，如果文件不存在，我只会得到一个损坏的图像占位符...

$('#myTheme').change
(
    function() 
    {
    var myImage = $('#myTheme :selected').text();
    $('.selectedImage img').attr('src','../wp-content/themes/myTheme/styles/'+myImage+'/screenshot.jpg');
    //if screenshot.jpg does not exist, use "../../default.jpg" instead
    }
);

Answer 1

听起来您需要访问 HTTP 响应 header 。这是我在网上找到的一段代码。

来源:http://www.vfstech.com/?cat=1

$(document).ready(function() {
   var ajaxSubmitOptions = {
      // the normal success callback is not used
      // success: function (responseText) {
      //      ...
      // } ,
      complete: function (xhrObj, status) {   
         if(status == "error") { // 500 server error?
            alert("There was an error processing this request.");
         } else {
            if (xhrObj.getResponseHeader("X-My-Custom-Header") != "") {            
               alert("Intercepted special HTTP header...");
               alert(xhrObj.getResponseHeader("X-My-Custom-Header"));
            }
            else {
               // call the function you normally would have used in the "success" callback:
               this._success(xhrObj.responseText);
            }                  
         }
      } ,
      _success: function (responseText) {
         alert("Normal success callback...");
         alert(responseText);
      }
   };

   $('#myForm').ajaxForm(ajaxSubmitOptions);
})