A JaxGL Helper used by gist:1448410 to load and display a model from ajax and/or indexedDB

async_helper.js.coffee

Jax.getGlobal().AsyncHelper = Jax.Helper.create
  load_from_idb: (idb_name, os_name, key, onsuccess, onfailure) ->
    indexedDB = window.indexedDB || window.webkitIndexedDB || window.mozIndexedDB
    IDBTransaction = IDBTransaction || window.webkitIDBTransaction
    IDBKeyRange = IDBKeyRange || window.webkitIDBKeyRange
    
    idb_request = indexedDB.open @indexedDB
    idb_request.onsuccess = (e) =>
      idb = e.target.result
      if idb.objectStoreNames.contains @objectStore
        active_store = idb.transaction([@objectStore], IDBTransaction.READ_WRITE).objectStore(@objectStore)
        get_request = active_store.get @key
        get_request.onsuccess = (e) =>
          if e.target.result
            onsuccess e.target.result.model_data
          else onfailure
        get_request.onerror = (e) ->
          console.log "ERROR: Unable to retrieve data"
          onfailure
      else onfailure
    idb_request.onerror = (e) ->
      console.log "ERROR: Unable to open indexedDB"
      onfailure
  
  
  save_to_idb: (idb, v, os, key, data) ->
    # idb is a database
    # os is the name of an objectstore which will be created if it doesn't exist
    
    if idb.objectStoreNames.contains os
      active_store = idb.transaction([os], IDBTransaction.READ_WRITE).objectStore(os)
      put_request = active_store.put { key: key, model_data: data }
      put_request.onsuccess = (e) -> console.log "Data stored in indexedDB"
      put_request.error = (e) -> console.log "Error putting data"; console.log e
     
    else
      version_request = idb.setVersion v
      version_request.onsuccess = (e) =>
        active_store = idb.createObjectStore os, { keyPath: "key" }
        put_request = active_store.put { key: key, model_data: data }
        put_request.onsuccess = (e) -> console.log "Data stored in indexedDB"
        put_request.error = (e) -> console.log "Error putting data"; console.log e
      version_request.onblocked = (e) -> console.log "Blocked setting version"; console.log e
      version_request.onerror = (e) -> console.log "Error setting version"; console.log e
      version_request.onfailure = (e) -> console.log "Failure setting version"; console.log e
  
  
  load_json: (json_path, callback) ->
    xhr = new XMLHttpRequest
    xhr.onreadystatechange = =>
      if xhr.readyState == 4 # request complete
        if xhr.status == 200 # request successful
          loaded_data = JSON.parse xhr.responseText
          callback loaded_data
        else # request erred
          throw new Error "XHR error: "+xhr.status+" for "+json_path
    xhr.open 'get', json_path, true
    xhr.send null