javascript传递变量和范围

Question

I am developing an web app and i need to play audio files. In this case I'm trying to create an object that will merge audio object properties, methods and events with some custom methods.

I have the following Object created:

<script type="text/javascript">
var AUDIO = {
    track: false,
    init: function(audioElement, fn) {
        var _this = this;
            _this.track = document.getElementById(audioElement) || false;

        if (!window.HTMLAudioElement) {
            alert(HELPER.translate('audio-load-error'));
            _this.track = false;
        }
        else {
            AUDIO.track.onloadedmetadata = (function() {
                _this.callback(fn);
            })();
        }

        return _this.track;  
    },
    on: function(eventName,fn) {
        var _this = this;   
        var listener = function(event) {
            _this.track.removeEventListener(eventName, listener, false);       
        }
        _this.track.addEventListener(eventName, listener, false);
    },
    callback: function(fn) {
        if (typeof fn == 'function') fn.call(this);
        if (typeof fn == 'object') $.execCallback(fn);      
    }

}
</script>

OK, now I call my methods something like this:

<script type="text/javascript">
AUDIO.init('audio-course', function(){
    console.log(AUDIO.track);
});
</script>

What I want is that is possible to pass AUDIO.track as a returned variable by AUDIO.init() so I can use something like this?:

<script type="text/javascript">
AUDIO.init('audio-course', function(returnedAudioObject){
    console.log(returnedAudioObject.duration);
});
</script>

If this is possible, please let me know the easiest way to do this. Thanks in advance!

Answer 1

I think you just want this?

if (typeof fn == 'function') fn.call(this, this.track)

Then returnedAudioObject will be AUDIO.track .