add this object into array

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Javascript infamous Loop problem?

for (var i=0; i<songList.length; i++){
        test.init({
        });
}

var test = {
    init: function (params) {
        var my = this;

        var backend = WaveSurfer.Audio;

        if (!params.predrawn) {
            backend = WaveSurfer.WebAudio;
        }
        var id = playList.length;
        this.id = id;

        this.backend = Object.create(backend);
        this.backend.init(params);

        this.drawer = Object.create(WaveSurfer.Drawer);
        this.drawer.init(params);

        this.backend.bindUpdate(function () {
            my.onAudioProcess();
        });

        this.bindClick(params.canvas, function (percents) {
            my.playAt(percents);
        });

    playList.push(my);

When I debug this script: my id is 0 for the first element; but when I go into the second loop suddenly both ids become 1. How is this possible?

enter image description here

So... you add an element to playlist, and you're confused that it's 1 element larger? — Wug, Nov 08 '12 at 20:56
No i'm confused about the fact that they have both id:1 when I expect the first to be 0 and the second to be 1 — Thomas, Nov 08 '12 at 20:58
@ThomasVerbeke code has 'this.id = id' which sets id as 1 for my — Amareswar, Nov 08 '12 at 21:01
@ThomasVerbeke: `this` and therefore `my` will be a reference to the same `test` object in every call. — I Hate Lazy, Nov 08 '12 at 21:03

Anoop · Answer 1 · 2012-11-08T21:02:52.890

Because first time playList is empty that why length of playlist is zero but after init call it has one items so length of playList become 1 for second init call so value of id depends on number of init call.

Since you are not creating any new object so every time my will reference same object. so any change in my will reflect in all pushed items in playlist.

Modified code: if you want add new item on each init call

var test = {
    init: function (params) {
        var my = {};

        var backend = WaveSurfer.Audio;

        if (!params.predrawn) {
            backend = WaveSurfer.WebAudio;
        }
        var id = playList.length;
        my.id = id;

        my.backend = Object.create(backend);
        my.backend.init(params);

        my.drawer = Object.create(WaveSurfer.Drawer);
        my.drawer.init(params);

        my.backend.bindUpdate(function () {
            my.onAudioProcess();
        });

        my.bindClick(params.canvas, function (percents) {
            my.playAt(percents);
        });

    playList.push(my);

add this object into array

1 Answers1