Question

注入了第三方javascript，它会在构建特定路径的某些逻辑之后创建一个新的Image（），但不会将其附加到文档中。

(function(){
    {....}
    new Image().src = "some_image_path";
})();

问题是我希望能够得到生成的“some_image_path”。我不知道要改变它什么，只是得到价值。我无法控制第三方JS并且无法更改。我尝试过使用cujojs / meld但它没有做任何事情或者出现“非法调用”错误。

有没有办法通过观察Image / HTMLImageElement对象或自动将onload属性添加到我定义的函数的所有Image实例来获得src值是什么？

Answer 1

您可以尝试使用自定义Image构造函数在闭包中加载第三方脚本。

(function() {
  var img;
  var Image = function Image() {
    return img = new (Function.prototype.bind.apply(window.Image, arguments));
  }

  // This is where the 3rd party code should be injected.
  // I'm assuming that since you're including it on your page, you know its source and trust it enough to `eval` it.
  // You won't be able to use a `<script>` tag to load it since that would execute in the global scope.
  // You'll likely need to use AJAX to fetch the script contents and pass to eval here.
  eval("new Image().src = some_image_path");

  return img;
})().src == some_image_path;

修改：

您可以覆盖全局Image（并且很好，然后再修复它）。由于脚本标签按顺序进行评估，因此应该可以使用。

<script> var img; var oldImage = Image; Image = function Image() { return img = new (Function.prototype.bind.apply(oldImage, arguments)); } </script> <script src="..."></script> <script> // img now contains the instantiated `Image` object img.src; // do what you will with this // Clean up Image = oldImage; </script>

Javascript添加侦听器或自动向所有新的Image（）实例添加属性

1 个答案: