#bottom_float{
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.9);
    box-shadow: 0px 1px 4px #e1e5e9;
}
#bottom_float .tk-div{
    background-color: #FFF;
    text-align: center;
    -webkit-box-align: center;
    margin: 10px auto;
}
.btn {min-width: 75px; font-size: 14px; margin: 0 3px;padding: .1rem .75rem;border-radius: 2px;height: 32px;cursor:pointer;}
.btn-primary {color: #fff;background-color: #4A90E2;border-color: #4A90E2; height: 40px;border-radius: 5px;transition: all .3s cubic-bezier(.645,.045,.355,1);}
.btn-primary.disabled{background-color: #999 !important;border-color: #999 !important;}
.btn-primary:hover {background-color: #7FB6F7;border-color: #7FB6F7;}

<div id="bottom_float">
    <div class="tk-div"><button type="button" id="print_btn" class="btn btn-primary">打印</button></div>
</div>

<script>
    document.getElementById("print_btn").addEventListener('click', function (evt) {
        //if (!evt.ctrlKey || (evt.key !== 'p' && evt.keyCode !== 80)) { return }
        evt.preventDefault()

        // ....
        window.print()

    })
</script>