SOURCE

$(function () {
    $('.btn1').click(function() {
        var qr   = $('.qrcode'),
            oUrl = $('.p1 input').val();
        qr.empty().qrcode({
            text: oUrl,                //任意内容
            render: 'canvas',          //渲染方式:table 或 canvas, 默认:canvas
            width: 240,
            height: 240,
            background: '#fff',
            foreground: '#000'

        });
    });
});

<div class="wrapper">
    <h1>二维码生成器</h1>
    <div class="qrcode"></div>
    <p class="p1"><input type="text" placeholder="http://"></p>
    <button class="btn1">立即生成二维码</button>
</div>

/*css reset */
body,p,div,ol,ul,li,dl,dt,dd,h1,h2,h3,h4,h5,h6,form,input,iframe,nav {
    margin: 0;
    padding: 0;
}
body {
    font: 16px Microsoft YaHei;
} 
a {
    text-decoration: none; 
} 
ol,ul {
    list-style: none;
} 

.wrapper {
    width: 500px;
    margin: 100px auto;
}
.wrapper h1 {
    text-align: center;
    color: #333;
    margin: 30px auto;
    font: 20px Microsoft YaHei;
}
.qrcode {
    width: 240px;
    height: 240px;
    background: #fff;
    padding: 20px;
    border: 1px solid #ddd;
    margin: 0 auto;
}
.p1 {
    width: 100%;
    margin: 30px auto;
    text-align: center;
}
.p1 input {
    outline: none;
    width: 100%;
    height: 38px;
    border: 1px solid #ccc;
    font-size: 16px;
    border-radius: 3px;
    box-sizing: border-box;
    padding: 0 10px;
    color: #666;
    transition: .6s;
}
.p1 input:focus {
    border: 1px solid #0ae;
}
.btn1 {
    display: block;
    width: 125px;
    height: 40px;
    background: #0ae;
    font: 14px Microsoft YaHei;
    margin: 20px auto 0 auto;
    border-radius: 5px;
    outline: none;
    border: 0;
    color: #fff;
    cursor: pointer;
    transition: .5s;
}
.btn1:hover {
    background: #09d;
}