What you want is a combination of yield and Deferreds (from jquery for example).
It's called sometimes pseudoThreads, Light Threading or Green Threads. And you can do exactly what you want with them in javascript > 1.7 . And here is how:
You'll need first to include this code:
$$ = function (generator) {
var d = $.Deferred();
var iter;
var recall = function() {
try {var def = iter.send.apply(iter, arguments);} catch(e) {
if (e instanceof StopIteration) {d.resolve(); return;}
if (e instanceof ReturnValueException) {
d.resolve(e.retval); return
};
throw e;
};
$.when(def).then(recall); // close the loop !
};
return function(arguments) {
iter = generator.apply(generator, arguments);
var def = iter.next(); // init iterator
$.when(def).then(recall); // loop in all yields
return d.promise(); // return a deferred
}
}
ReturnValueException = function (r) {this.retval = r; return this; };
Return = function (retval) {throw new ReturnValueException(retval);};
And of course call jquery code to get the $ JQuery acces (for Deferreds).
Then you'll be able to define once for all a Sleep function:
function Sleep(time) {
var def = $.Deferred();
setTimeout(function() {def.resolve();}, time);
return def.promise();
}
And use it (along with other function that could take sometime):
// Sample function that take 3 seconds to execute
fakeAjaxCall = $$(function () {
yield (Sleep(3000));
Return("AJAX OK");
});
And there's a fully featured demo function:
function log(msg) {$('<div>'+msg+'</div>').appendTo($("#log")); }
demoFunction = $$(function (arg1, arg2) {
var args = [].splice.call(arguments,0);
log("Launched, arguments: " + args.join(", "));
log("before sleep for 3secs...");
yield (Sleep(3000));
log("after sleep for 3secs.");
log("before call of fake AjaxCall...");
ajaxAnswer = yield (fakeAjaxCall());
log("after call of fake AjaxCall, answer:" + ajaxAnswer);
// You cannot use return, You'll have to use this special return
// function to return a value
log("returning 'OK'.");
Return("OK");
log("should not see this.");
});
As you can see, syntax is a little bit different:
Remember:
- any function that should have these features should be wrapped in
$$(myFunc)
$$ will catch any yielded value from your function and resume it only when
the yielded value has finished to be calculted. If it's not a defered, it'll work
also. - Use 'Return' to return a value.
- This will work only with Javascript 1.7 (which is supported in newer firefox version)
