Reading qrcode issue on webpage

I got all required js libs from http://ift.tt/1ECCM97

and put into my project/js folder. Then I created a simple index.html with this:

<div id="reader" style="width:300;height:250px">
</div>

$(document).ready(function () {

    $('#reader').html5_qrcode(function (data) {
        alert(data);
    },
    function (error) {
        console.log(error);
    }, function (videoError) {
        console.log(videoError);
    });

});

I can see the picture of my camera (online,moving) but it does not scan any qrcode. Why?

I use my laptop's webcam. Is it bacause of the inversed picture of the camera?

I have seen videos where others tried it and was working. e.g. here on the bottom of the page: http://ift.tt/2xhOOaT