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Caching Dynamically Loaded Images

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I'm using javascript to dynamically load any of a series of images into a single img tag, based on user interaction: function reassignImage(newSource) { img.src = newSource; }

Solution 1:

What's the cache-control header set to in the http response for the image? (Chrome developer tools will show you). If it's not set to be cacheable, it will get refetched.

Solution 2:

This will pre-load an image so that the browser can display it immediately when you actually set the src of an img tag. I speculate that pre-loading an image like this will ensure it's in the cache so it won't reload, though I haven't tested it.

var myImg = new Image(25, 25);
myImg.src = "/foobar.png";

In other words, this should now hopefully only download two images

functionreassignImage(newSource) {
    var myImg = newImage(25, 25);
    myImg.src = newSource;
    img.src = newSource;
}

reassignImage("first.png");
reassignImage("second.png");
reassignImage("first.png");

Edit

I was doing it wrong. Try creating a new Image() for every new file the user loads. Swap these image elements in and out of the dom.

<html><head><script>var imageElements = {};
    functionreassignImage(newSource) {
      if (typeof imageElements[newSource] == "undefined") {
        imageElements[newSource] = newImage();
        imageElements[newSource].src = newSource;
      }
      var container = document.getElementById("imageContainer");
      container.innerHTML = '';
      container.appendChild(imageElements[newSource]);
    }
    </script></head><body><divid="imageContainer"></div></body></html>

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