Creating events in Javascript

Question

If I have a list of functions that are serving as event subscriptions, is there an advantage to running through them and calling them with .call() (B below), or more directly (A)? The code is below. The only difference I can see is that with .call you can control what this is set to. Is there any other difference besides that?

    $(function() {
        eventRaiser.subscribe(function() { alert("Hello"); });
        eventRaiser.subscribe(function(dt) { alert(dt.toString()); });

        eventRaiser.DoIt();
    });

    var eventRaiser = new (function() {
        var events = [];
        this.subscribe = function(func) {
            events.push(func);
        };

        this.DoIt = function() {
            var now = new Date();
            alert("Doing Something Useful");
            for (var i = 0; i < events.length; i++) {
                events[i](now);  //A
                events[i].call(this, now);  //B
            }
        };
    })();

Felix Kling · Accepted Answer · 2011-09-15 16:22:15Z

3

No, there is no other difference. If you follow the second approach though, you can extend subscribe so that the "clients" can specify the context to be used:

this.subscribe = function(func, context) {
     events.push({func: func, context: context || this});
};

this.DoIt = function() {
    var now = new Date();
    alert("Doing Something Useful");
    for (var i = 0; i < events.length; i++) {
        events[i].func.call(events[i].context, now);
    }
 };

answered Sep 15, 2011 at 16:22

Felix Kling

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Comments

beefyhalo · Accepted Answer · 2011-09-15 16:37:41Z

1

If you decide to go with method B, you can allow the function that subscribes to the event, to perform event specific functions.

For instance, you could use this.getDate() inside your function (you would have to create the method) instead of passing the date as a parameter. Another helpful method inside an Event class would be this.getTarget().

answered Sep 15, 2011 at 16:37

beefyhalo

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