$('#note').elastic();

更新：似乎不再有elastic.js，但是如果您正在寻找一个外部库

autosize(document.getElementById("note"));


textarea#note {

    width:100%;

    box-sizing:border-box;

    direction:rtl;

    display:block;

    max-width:100%;

    line-height:1.5;

    padding:15px 15px 30px;

    border-radius:3px;

    border:1px solid #F7E98D;

    font:13px Tahoma, cursive;

    transition:box-shadow 0.5s ease;

    box-shadow:0 4px 6px rgba(0,0,0,0.1);

    font-smoothing:subpixel-antialiased;

    background:linear-gradient(#F9EFAF, #F7E98D);

    background:-o-linear-gradient(#F9EFAF, #F7E98D);

    background:-ms-linear-gradient(#F9EFAF, #F7E98D);

    background:-moz-linear-gradient(#F9EFAF, #F7E98D);

    background:-webkit-linear-gradient(#F9EFAF, #F7E98D);

}


<script src="https://rawgit.com/jackmoore/autosize/master/dist/autosize.min.js"></script>

<textarea id="note">Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi.</textarea>