<textarea id="t1" class="myclass" style="e1">bbbbbb</textarea>
<textarea id="t2" class="myclass" style="e1">bbbbbb</textarea>
<textarea id="t3" class="myclass" style="e1">bbbbbb</textarea>
<div id="d1" style='max-width:500px;display: none'>bbbbbb</div>

$('body').on('keypress','.myclass' ,function() {
        $("#d1").text($(this).val());
        $(this).css("width", $("#d1").css("width"));
        this.style.overflow = 'hidden';
        this.style.height = 0;
        this.style.height = this.scrollHeight + 'px';
    })

.e1{
min-width:100px;
height:20px;
}