Adding Children to Container() EaselJS

I am going through some tutorials and experimenting with javascript and more particularly EaselJS. I want to create a number of containers which hold images and a text together. But I get the following error: "Uncaught TypeError: undefined is not a function" when I try to add the text and image to the container.

    function init() {
        stage = new createjs.Stage("demoCanvas");


        for(var i=0; i<container.length; i++) { //looping through creation of objects
            container[i] = new createjs.Container();
            container[i].x = Math.floor(Math.random() * (760 - 40));
            img[i] = new createjs.Bitmap (" choc.png" );
            container.addChild(img[i]);
            txt[i] = new createjs.Text(i, "bold 16px Courier", "#fff");
            txt[i].textAlign = "center";
            txt[i].y = 50;
            container.addChild(txt[i]);
            stage.addChild(container[i]);

        }

The errors is on the container.addChild(img[i]); line.