Question

I have this function which pings my server for a specific change in data:

function connected() {
  $.ajax({
    success : function(d) {
      if (d.success) {
        // return data
      } else {
        setTimeout(connected, 200);
      }
    }
  });
}

(Obviously the code has been stripped to the bare minimum to make my intentions clearer)

What I want to do is return a bool true when it gets found, so I can go

if (connected()) {
  // process data
}

(obviously the data is stored in a global variable.)

Is there any way to achieve this?

EDIT

I could create a ‘pause’ function:

function pauseScript(ms) {
  ms += new Date().getTime();
  while (new Date().getTime() < ms) {}
}

Then change my code to exclude setTimeout() (and include some other stuff)

function connected() {
  var value;
  $.ajax({
    async: false,
    success : function(d) {
      if (d.success) {
        // set data
          value = true;
      } else {
        pauseScript(200);
        value = connected();
      }
    }
  });
  return value;
}

However this feels a little hacky!

Answer 1

For doing that the best should continue in async mode :

function connected(callback) {
  $.ajax({
    success : function(d) {
      if (d.success) {
        callback();
      } else {
        setTimeout(function() {
          connected(callback);
        }, 200);
      }
    }
  });
}

//Using :
connected(function(){
  //Here i finish my scan result
});

Maybe, i’m not so sure in this case, you will need to bind this (I mean binding scope) :
http://www.robertsosinski.com/2009/04/28/binding-scope-in-javascript/