On Wed, Jul 23, 2014 at 4:49 PM, Paul bellamy <p...@appl.com.au> wrote: > In the specification for XMLHttpRequest you posted a “warning” about using > async=false which indicates that it is the intention to eventually remove > this feature due to “detrimental effects to the user experience” when in a > document environment. > > I understand that synchronous events retrieving data can, if not managed > properly in the code, cause delays to the flow of the parsing and display of > the document. This may, if the programming practices are poor, be > extrapolated to be “detrimental to the users experience”, however there are > times when there is a need to have data retrieved and passed synchronously > when dealing with applications. > > In business application development there will always be the situation of > the client needing to manipulate the display based on actions that retrieve > data or on previously retrieved data. In these cases it is necessary for the > data retrieval to be synchronous. > > If the document/form has to be resubmitted in full each time a client-side > action is taken or the client needs to retrieve data to decide what action > to take, then the user experience is definitely affected detrimentally as > the entire document needs to be uploaded, downloaded, parsed and displayed > again. Further there is the unnecessary need to retain instances of > variables describing the client-side environment on the server-side. > Variables which are not necessary for processing and should be handled by > the client.
This last paragraph suggests that you don't really understand what "asynchronous XHR" means. You appear to be equating it with submitting a form and loading a fresh page. Async XHR just means that .send() returns immediately, rather than pausing JS and waiting for the response to come back; the XHR object then fires an event on itself when the response comes back, which you have to listen for. ~TJ