Example Application Cache "Bootloader"

gistfile1.js

(function(){

  function useManifest(content){
    var tag;
    var stylesheets = content.match(/\/css\/.*\.css/g);
    for (var i=0; i<stylesheets.length; i++){
      tag = document.createElement('link');
      tag.href = stylesheets[i];
      tag.rel = "stylesheet";
      document.getElementsByTagName('head')[0].appendChild(tag);
    }
    var scripts = content.match(/\/js\/.*\.js/g);
    var loadedCount = 0;
    function didLoad(){
      loadedCount += 1;
      if (loadedCount == scripts.length){
        var global = (function(){return this;})();
        global.bootloadedManifest = {
          scripts: scripts,
          stylesheets: stylesheets,
          body: content
        };
        require('main');
      }
    }
    for (i=0; i<scripts.length; i++) {
      // This is where you can choose to skip over certain Javascript files 
      // that appear in the manifest -- in this case, a web worker runtime
      if (/\bworker\b/.test(scripts[i])){
        loadedCount +=1;
      } else {
        tag = document.createElement('script');
        tag.src = scripts[i];
        tag.type = "text/javascript";
        tag.onload = didLoad;
        document.getElementsByTagName('head')[0].appendChild(tag);
      }
    }
  }


  function retrieveManifest(cb){
    var req = new XMLHttpRequest();
    req.open("GET",document.documentElement.getAttribute('manifest'),true);
    req.onreadystatechange = function(){
      if (req.readyState === req.DONE){
        if (req.status === 200){
          cb(req.response);
        } else {
          throw new Error("failed to retrieve manifest");
        }
      }
    };
    req.send();
  }

  // In development, you don't want to be running out of an actual 
  // application cache, because you need to reload all the time. But
  // we do want to test everything under the bootloader. So this lets
  // you provide a fake manifest file within a <script type="text/fake-manifest"> 
  // tag.
  function retrieveFakeManifest(cb){
    var content = document.querySelector('script[type="text/fake-manifest"]').innerHTML;
    if (content)
      cb(content);
    else
      throw new Error("no fake manifest available");
  }
  
  if (document.documentElement.getAttribute('manifest')){
    retrieveManifest(useManifest);
  } else {
    retrieveFakeManifest(useManifest);
  }
})();

Looks promising. Have you had many use cases where appcache was very useful in these modern times where internet is readily available?