Untitled

<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">

</head>

<body>

    <input id="text" type="text" value="https://hogangnono.com" style="width:80%" /><br />
    <div id="qrcode"></div>

<script type="text/javascript" src="javascripts/qrcode.min.js">

var qrcode = new QRCode("qrcode");

function makeCode () {
    var elText = document.getElementById("text");

    if (!elText.value) {
        alert("Input a text");
        elText.focus();
        return;
    }

    qrcode.makeCode(elText.value);
}

makeCode();

$("#text").
    on("blur", function () {
        makeCode();
    }).
    on("keydown", function (e) {
        if (e.keyCode == 13) {
            makeCode();
        }
    });
</script>

</body>
</html>