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。
用了在上继续封装的，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();});
