row auto textarea

function auto_grow(element) {
    element.style.height = "5px";
    element.style.height = (element.scrollHeight)+"px";
}

<textarea oninput="auto_grow(this)"></textarea>
 Run code snippet

textarea {
    resize: none;
    overflow: hidden;
    min-height: 50px;
    max-height: 100px;
}