Javascript 检查图像源已加载

发布于 2024-08-18 05:35:05 字数 1131 浏览 9 评论 0原文

我一直在尝试让它工作，但没有 100% 成功，基本上是尝试加载图像，如果源不存在，请尝试第二个图像，直到达到默认图像。

我一直在尝试基于这个问题，但是我没有使用 jQuery，所以接受的解决方案对我来说没有用，所以尝试第二个解决方案，它几乎有效，但似乎不起作用（如果这有意义吗？）。我可以用它来测试我们需要的第二个图像，但它似乎不会再次触发 onload 事件。

function topTenImages(){
 var topTenDiv = document.getElementById('toptenimg');
 var topTenImg = new Image();
 var ac = "tryout";
 var imageOrder = new Array(
  "/images/codespec/banners/"+ac+"_topten.gif",
  "/images/codespec/banners/"+ac+"_topten.jpg",
  "/images/banners/default_topten.png",
  "/images/banners/default_topten.jpg"
 );
 var errorCnt = 0;
 topTenImg.src = domainResources+imageOrder[errorCnt];
 topTenImg.onLoad = new function(){
  if(!checkImage(topTenImg)){
   if(errorCnt &lt; imageOrder.length){
    var io = imageOrder[++errorCnt];
    topTenImg.src = domainResources+io;
   }
  }
 }
 topTenDiv.appendChild(topTenImg);
}

是的，我知道我们可以使用 php/perl/et al 来完成此服务器端，但我们正在尝试限制我们的传出标头，所以这似乎是最好的方法。（欢迎替代方案）。我的另一个想法是将其包装在数组上的 for 循环中，并每次创建一个新对象。但这似乎更有意义。

谢谢，心理

原文

I've been trying to get this working, and not having 100% success, basically trying to load an image, if the source doesn't exist try a second image until it reaches a default one.

I have been trying the solution based on this question, however I am not using jQuery, so the accepted solution is no use to me, so trying the 2nd solution, which pretty much works, but doesn't seem to be (if that makes sense?). I can get it to test the second image we need, but then it doesn't seem to trigger the onload event again.

function topTenImages(){
 var topTenDiv = document.getElementById('toptenimg');
 var topTenImg = new Image();
 var ac = "tryout";
 var imageOrder = new Array(
  "/images/codespec/banners/"+ac+"_topten.gif",
  "/images/codespec/banners/"+ac+"_topten.jpg",
  "/images/banners/default_topten.png",
  "/images/banners/default_topten.jpg"
 );
 var errorCnt = 0;
 topTenImg.src = domainResources+imageOrder[errorCnt];
 topTenImg.onLoad = new function(){
  if(!checkImage(topTenImg)){
   if(errorCnt < imageOrder.length){
    var io = imageOrder[++errorCnt];
    topTenImg.src = domainResources+io;
   }
  }
 }
 topTenDiv.appendChild(topTenImg);
}

Yes I know that we could do this server side with php/perl/et al, but we are trying to limit our outgoing headers, so this seemed to be the best way of doing it. (Alternatives welcome). My other thought was to wrap it in a for loop on the array, and create a new object each time. But this seemed to make more sense.

Thanks,
Psy

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懒的傷心 2024-08-25 05:35:05

这应该回答你的问题：
http://www.thefutureoftheweb.com/blog/image-onload-未被调用
你只需要先设置onLoad即可。希望这会起作用：

 topTenImg.onLoad = function(){
  if(!checkImage(topTenImg)){
   if(errorCnt < imageOrder.length){
    var io = imageOrder[++errorCnt];
    topTenImg.src = domainResources+io;
   }
  }
 }
 topTenImg.src = domainResources+imageOrder[errorCnt];

This should answer your question:
http://www.thefutureoftheweb.com/blog/image-onload-isnt-being-called
You just need to set onLoad first. Hopefully that will work:

 topTenImg.onLoad = function(){
  if(!checkImage(topTenImg)){
   if(errorCnt < imageOrder.length){
    var io = imageOrder[++errorCnt];
    topTenImg.src = domainResources+io;
   }
  }
 }
 topTenImg.src = domainResources+imageOrder[errorCnt];

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