Check the existence of an image file at `url` by creating a temporary Image element.

checkImage.example.js

// Example Use
(function () {

  function success() {
    console.log("success: ", this.src);
  }

  function failure() {
    console.log("failure: ", this.src);
  }

  // this fails
  checkImage("http://www.google.com/", success, failure);

  // this succeeds
  checkImage("http://www.google.com/intl/en_com/images/srpr/logo3w.png", success, failure);

})();

checkImage.js

(function (window) {

  // Stores past URLs that failed to load. Used for a quick lookup
  // and because `onerror` is not triggered in some browsers
  // if the response is cached.
  var errors = {};

  // Check the existence of an image file at `url` by creating a
  // temporary Image element. The `success` callback is called
  // if the image loads correctly or the image is already complete.
  // The `failure` callback is called if the image fails to load
  // or has failed to load in the past.
  window.checkImage = function (url, success, failure) {
    var img = new Image(),    // the 
        loaded = false,
        errored = false;

    // Run only once, when `loaded` is false. If `success` is a
    // function, it is called with `img` as the context.
    img.onload = function () {
      if (loaded) {
        return;
      }

      loaded = true;

      if (success && success.call) {
        success.call(img);
      }
    };

    // Run only once, when `errored` is false. If `failure` is a
    // function, it is called with `img` as the context.
    img.onerror = function () {
      if (errored) {
        return;
      }

      errors[url] = errored = true;

      if (failure && failure.call) {
        failure.call(img);
      }
    };

    // If `url` is in the `errors` object, trigger the `onerror`
    // callback.
    if (errors[url]) {
      img.onerror.call(img);
      return;
    }
    
    // Set the img src to trigger loading
    img.src = url;

    // If the image is already complete (i.e. cached), trigger the
    // `onload` callback.
    if (img.complete) {
      img.onload.call(img);
    }
  };

})(this);

Very nice. But what's the point of checking for errors[url] after setting the img.src? It seems as if that will make the browser go ahead and try and download the image again for no reason, if you know you're just going to error out if you've already discovered it doesn't exist. My small change therefore (using this in my own code) was to swap lines 50-52 with line 46, and return after "img.onerror.call(img);", to hard-abort and give up instead of forcing the browser to make another request.

Thanks for this. That was an oversight on my part.

Nice and simple solution!

If error occur, is it possible to get error message like error 404 (Not Found) or 401 (Authorization Required)?
I can read error in console log, but is it possible to display error on web page or store it in database for later use...

Thank you in advance.

@Amilino: as far as I know, img.onerror doesn't provide you with useful information such as the response code from the server. To do that, I think you would need to do an AJAX request for the image. This would give you the complete response.