When do I use a synchronous versus a asynchronous request?
Asynchronous is more complex to manage, many prefer using XMLHttpRequest in Synchronous mode which could have a negative effect specially on high load or slow website link, because the JavaScript engine is blocked until the request completes. That’s why today we use AJAX and not SJAX, and the complexity of asynchronous programming is better handled today with the multitude of frameworks and techniques which make AJAX interfaces more fluid.