discourse/app/assets/javascripts/preload_store.js

/* We can insert data into the PreloadStore when the document is loaded.
   The data can be accessed once by a key, after which it is removed */
PreloadStore = {
  data: {},
  store: function(key, value) {
    this.data[key] = value;
  },
  /* To retrieve a key, you provide the key you want, plus a finder to
     load it if the key cannot be found. Once the key is used once, it is
     removed from the store. So, for example, you can't load a preloaded topic
     more than once. */
  get: function(key, finder) {
    var promise, result;
    promise = new RSVP.Promise();
    if (this.data[key]) {
      promise.resolve(this.data[key]);
      delete this.data[key];
    } else {
      if (finder) {
        result = finder();

        // If the finder returns a promise, we support that too
        if (result.then) {
          result.then(function(result) {
            return promise.resolve(result);
          }, function(result) {
            return promise.reject(result);
          });
        } else {
          promise.resolve(result);
        }
      } else {
        promise.resolve(void 0);
      }
    }
    return promise;
  },
  /* Does the store contain a particular key? Does not delete, just returns
     true or false. */
  contains: function(key) {
    return this.data[key] !== void 0;
  },
  /* If we are sure it's preloaded, we don't have to supply a finder. Just
     returns undefined if it's not in the store. */
  getStatic: function(key) {
    var result;
    result = this.data[key];
    delete this.data[key];
    return result;
  }
};