Return the response from an function call

Synchronous function

Everything after value = sincFunction(); will wait until sincFunction() will execute and it will return a result.
function sincFunction() {
  var value;
  while(...) {
   // do something
  }
  return value;
}
var value = sincFunction();
// Do something with item
doSomethingElse();


Asynchronous function

This is the opposite of the synchronous function, in this case there will not be any waiting on execution for the asincFunction function. Using a callback you can retrieve the response after the function is completed and you have the result.
asincFunction(function(value) {
  // do something
});
doSomethingElse();