Question

我如何检查给定的网址是否有效图像，如果无效则为404（404），然后在20秒后重新检查并使用Javasript尝试这样5分钟

checkFileExists = function(){
    $.ajax({
        type: 'HEAD',
        url: fileUrl,
        crossDomain: true,
        success: function(response) {
          // Further processing if file exists
          fileExists = true;
          console.log(response);
        },
        error: function(error) {
            // File does not exists, run through function again-
          console.log(error);
          fileExists = false;
        }
    });
  }



if(!fileExists) {
   setTimeout(function(){
      checkFileExists();
   }, 20000);
}

但是它不起作用会抛出错误'XMLHttpRequest无法加载XXXX否请求的资源上存在'Access-Control-Allow-Origin'标题。'

**我的文件网址是'https://drive.google.com/thumbnail?xxxx'我从我的localhost请求

Answer 1

尝试在函数checkFileExists中创建新的img元素，设置url图像并设置onError事件函数。

＆＃13;

var checkImage = function(url){
    console.log("1");
    var s = document.createElement("IMG");
    s.src = url
    s.onerror = function(){
  		console.log("file with "+url+" invalid");
        alert("file with "+url+" invalid")
    }
    s.onload = function(){
        console.log("file with "+url+" valid");
        alert("file with "+url+" valid")
    }
}

checkImage("http://ya.ru/favic2on.ico")

＆＃13;

More info

Answer 2

我找到了两种有趣的方法来检查网络上的图片网址是否损坏：

function isImageOk(img) {
    // During the onload event, IE correctly identifies any images that
    // weren't downloaded as not complete. Others should too. Gecko-based
    // browsers act like NS4 in that they report this incorrectly.
    if (!img.complete) {
        return false;
    }

    // However, they do have two very useful properties: naturalWidth and
    // naturalHeight. These give the true size of the image. If it failed
    // to load, either of these should be zero.
    if (typeof img.naturalWidth != "undefined" && img.naturalWidth == 0) {
        return false;
    }

    // No other way of checking: assume it's ok.
    return true;
}

当页面加载时，我们遍历images []数组以检查它们。

addEvent(window, "load", function() {
    for (var i = 0; i < document.images.length; i++) {
        if (!isImageOk(document.images[i])) {
            document.images[i].style.visibility = "hidden";
        }
    }
});

为了在20秒间隔内检查URL，您可以在循环中使用javascript的setTimeout（）函数。

(function(){
    // do some stuff
    setTimeout(arguments.callee, 60000);
})();

您可以查看此链接：Calling a function every 60 seconds，了解有关每隔X秒调用一次函数的详细信息。

检查图像网址是有效还是已损坏

2 个答案: