css部分

#textarea {    display: block;    margin:0 auto;    overflow: hidden;    width: 550px;    font-size: 14px;    height: 18px;    line-height: 24px;    padding:2px;}textarea {    outline: 0 none;    border-color: rgba(82, 168, 236, 0.8);    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1), 0 0 8px rgba(82, 168, 236, 0.6);}

js代码

/*** 文本框根据输入内容自适应高度* @param                {HTMLElement}        输入框元素* @param                {Number}                设置光标与输入框保持的距离(默认0)* @param                {Number}                设置最大高度(可选)*/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();};

　　html部分  包含调用