方法一:

<textarea rows=1 cols=40 style='overflow:scroll;overflow-y:hidden;;overflow-x:hidden'
onfocus="window.activeobj=this;this.clock=setInterval(function(){activeobj.style.height=activeobj.scrollHeight+'px';},200);" onblur="clearInterval(this.clock);"></textarea>

方法二：

<script>
var agt = navigator.userAgent.toLowerCase();
var is_op = (agt.indexOf("opera") != -1);
var is_ie = (agt.indexOf("msie") != -1) && document.all && !is_op;
function ResizeTextarea(a,row){
    if(!a){return}
    if(!row)
        row=5;
    var b=a.value.split("\n");
    var c=is_ie?1:0;
    c+=b.length;
    var d=a.cols;
    if(d<=20){d=40}
    for(var e=0;e<b.length;e++){
        if(b[e].length>=d){
            c+=Math.ceil(b[e].length/d)
        }
    }
    c=Math.max(c,row);
    if(c!=a.rows){
        a.rows=c;
    }
}
</script>
<textarea style="overflow: hidden;  font-family: Verdana,Arial; font-style: normal;  font-size: 13px; line-height: normal; " rows="4" cols="30" onfocus="javascript:ResizeTextarea(this,4);" onclick="javascript:ResizeTextarea(this,4);" onkeyup="javascript:ResizeTextarea(this,4);"></textarea>

〖常用代码〗Tags: 文本框 textarea 自适应 自适应高度