Question

I’m trying to have my backbone application check the server as often as possible for updates to a model, similar to how twitter’s site has new tweets that are automatically added.

My current setup is checking an external application through their api so I have no access to their server which leaves me to rely on the client side to do the checking without being too memory hungry, how can I achieve this?

Answer 1

In Javascript the only way you can really control timing is through setTimeout/setInterval; there is no “more sophisticated” mechanism, unless you count helper functions (eg. ‘delay’) which just wrap setTimeout/setInterval.

So, dmi3y’s answer was correct. However, since you mentioned Backbone in both the tags and in the description, here’s a more Backbone-ish version…

var YourModelClass = Backbone.Model.extend({url: remoteUrl});
var instance = new YourModelClass();
var seconds = 5;
window.setInterval(_.bind(instance.fetch, instance), 1000 * seconds);

or, if you wanted to build it in to your class …

var YourModelClass = Backbone.Model.extend({
    url: remoteUrl,
    initialize: function() {
        var seconds = 5;
        window.setInterval(_.bind(this.fetch, this), 1000 * seconds);
    }
});
var instance = new YourModelClass();

It’s also worth mentioning that setInterval returns an object which you can pass to clearInterval if you want to stop “polling”.

P.S. Just in case you’re not familiar with _.bind, it comes from the Underscore library, which Backbone depends on so you already have it. All it does is fix this in place, so that when your timeout/interval function resolves, the this inside it will be the second argument to _.bind (and not window, which is what it would normally be).