js实现多行文本框textarea自适应

实现思路：获取元素内容高度scrollHeight（滚动高度），当元素状态改变时调用 函数（当需求高度大于实际高度时，更新实际高度为内容高度）

 <textarea name="textArea" id="t1"></textarea>

var textArea1 = document.getElementById('t1');
function activeGo() {
    //内容高度，实际高度，实际高度变成内容高度
    var scrollHeight = textArea1.scrollHeight;
    var height = textArea1.offsetHeight;
    //alert("需求高度px"+scrollHeight);
    //alert("实际高度"+height);
    if(height < scrollHeight){
        textArea1.style.height = textArea1.scrollHeight+'px';
        //alert("转换高度"+textArea1.style.height);
    }
}
//添加属性改变、输入事件监听
    textArea1.addEventListener('propertychange',activeGo);
    textArea1.addEventListener('input',activeGo);

textarea高度自适应结束，以下是工作中的问题。

用了在asp.net上继续封装的flowportal.net，其中的XTextBox组件没有相关便捷属性设置。所以如下实现自适应。

<form runat="server">
        <!-- Insert content here -->
        <table width="1066" border="0" cellspacing="0" cellpadding="0">
            <tbody>
                <tr>
                    <td width="266" colspan="2">
                        <aspxform:XTextBox id="XTextBox1" onkeydown="MutilineTextBox()" runat="server" BorderColor="#DCDCDC" BorderWidth="1" TextMode="MultiLine" XDataBind="vHeight" Width="100%"></aspxform:XTextBox>
                    </td>
                    <td width="266">
                    </td>
                    <td width="267">
                    </td>
                </tr>
                <tr>
                    <td>
                    </td>
                    <td width="266">
                    </td>
                    <td>
                    </td>
                    <td>
                    </td>
                </tr>
                <tr>
                    <td>
                    </td>
                    <td width="266">
                    </td>
                    <td>
                    </td>
                    <td>
                    </td>
                </tr>
            </tbody>
        </table>
    </form>

var autoTextarea = function (elem, extra, maxHeight) {
        extra = extra || 0;
        var isFirefox = !!document.getBoxObjectFor || 'mozInnerScreenX' in window,
        isOpera = !!window.opera && !!window.opera.toString().indexOf('Opera'),
                addEvent = function (type, callback) {
                        elem.addEventListener ?
                                elem.addEventListener(type, callback, false) :
                                elem.attachEvent('on' + type, callback);
                },
                getStyle = elem.currentStyle ? function (name) {
                        var val = elem.currentStyle[name];

                        if (name === 'height' && val.search(/px/i) !== 1) {
                                var rect = elem.getBoundingClientRect();
                                return rect.bottom - rect.top -
                                        parseFloat(getStyle('paddingTop')) -
                                        parseFloat(getStyle('paddingBottom')) + 'px';
                        };

                        return val;
                } : function (name) {
                                return getComputedStyle(elem, null)[name];
                },
                minHeight = parseFloat(getStyle('height'));

        elem.style.resize = 'none';

        var change = function () {
                var scrollTop, height,
                        padding = 0,
                        style = elem.style;

                if (elem._length === elem.value.length) return;
                elem._length = elem.value.length;

                if (!isFirefox && !isOpera) {
                        padding = parseInt(getStyle('paddingTop')) + parseInt(getStyle('paddingBottom'));
                };
                scrollTop = document.body.scrollTop || document.documentElement.scrollTop;

                elem.style.height = minHeight + 'px';
                if (elem.scrollHeight > minHeight) {
                        if (maxHeight && elem.scrollHeight > maxHeight) {
                                height = maxHeight - padding;
                                style.overflowY = 'auto';
                        } else {
                                height = elem.scrollHeight - padding;
                                style.overflowY = 'hidden';
                        };
                        style.height = height + extra + 'px';
                        scrollTop += parseInt(style.height) - elem.currHeight;
                        document.body.scrollTop = scrollTop;
                        document.documentElement.scrollTop = scrollTop;
                        elem.currHeight = parseInt(style.height);
                };
        };

        addEvent('propertychange', change);
        addEvent('input', change);
        addEvent('focus', change);
        change();
};

        function MutilineTextBox() {
        //获取多行文本框
     var text = document.getElementById("XTextBox1").getElementsByTagName("textarea")[0];
      autoTextarea(text);// 调用
        }

        //加载时调用
        Ext.onReady(function () {
          MutilineTextBox();
        });