Out of Scope Objects in NodeJS

Question

I am using an audio-player package to play a sound locally when a node app triggers an event. When the event is triggered, a function is called with the specific file that needs to be opened as such:

playSound(fileName);

The separate function looks like this:

player = new Player('someDirectory/' + fileName + '.mp3');
player.play();

This opens and begins playing the file perfectly well, however when events trigger in quick succession, both sounds will be simultaneously playing. While I initially thought to simply add a:

player.stop();

before the 'new Player' definition, the previous instance is clearly out of scope, as the function has been called a second time. How can I stop all other instances of Player before starting playback anew?

katspaugh · Accepted Answer · 2014-11-28 08:54:24Z

1

You need to declare the player variable in the outer scope, so that every function "sees" the same player.

var player;

function playSound(fileName) {
    if (player) {
        player.stop();
    }

    player = new Player(fileName);
    player.play();
}

This is called a closure.

answered Nov 28, 2014 at 8:54

katspaugh

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1 Comment

JD Angerhofer Over a year ago

Ah, wonderful. I should have known to reassign player with every call. Thanks for the spot-on answer!

Oscar · Accepted Answer · 2014-11-28 08:43:41Z

0

Your player should be static, only one instance should exist and play all sounds.

function Podcast() {};

Podcast.FILE_EXTENSION = 'mp3';
Podcast.download = function(podcast) {
    console.log('Downloading ' + podcast + ' ...');
};

Here we created a constructor function named Podcast with a static property called FILE_EXTENSION and a static method named download.

http://elegantcode.com/2011/01/19/basic-javascript-part-7-static-properties-and-methods/

answered Nov 28, 2014 at 8:43

Oscar

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