But wait … there’s more!

“Waiting is one of the great arts.”
— Margery Allingham

Every once in a while, I will run into a situation where my code needs to wait for some other asynchronous process to complete. You don’t really want to go anywhere, and you don’t want to do anything. You just want to wait. On the client side, this is easily accomplished with a simple setTimeout. This is usually done with a basic recursive loop that repeats until the conditions are right to proceed.

function waitForSomething() {
	if (something) {
		itIsNowOkToProceed();
	} else {
		setTimeout(waitForSomething, 500);
	}
}

Unfortunately, on the server side, where this need usually arises, the setTimeout function is not available. However, there is a widely known, but poorly documented, GlideSystem function called sleep that you can use in the global scope to provide virtually the same purpose.

function waitForSomething() {
	if (something) {
		itIsNowOkToProceed();
	} else {
		gs.sleep(500);
		waitForSomething();
	}
}

Don’t try this in a scoped application, though, because you will just get a nasty message about how gs.sleep() is reserved for the global scope only. Fortunately, like a lot of things in ServiceNow, if you know the secret, you can get around such restrictions. In this case, all you really need is a Script Include that IS in the global scope, and then you can call that script from your scoped application and it will work just fine. Here is a simple example of just such as script:

var Sleeper = Class.create();
Sleeper.prototype = {
    initialize: function() {
    },

	sleep: function(ms) {
		gs.sleep(ms);
	},

    type: 'Sleeper'
};

Once you have your global-scoped Script Include set up, you can now call it from a scoped app and it will actually work.

function waitForSomething() {
	if (something) {
		itIsNowOkToProceed();
	} else {
		new global.Sleeper().sleep(500);
		waitForSomething();
	}
}