textarea如何實現高度自適應？

文章來源：http://blog.csdn.net/tianyitianyi1/article/details/49923069

 

 

轉自：http://www.xuanfengge.com/textarea-on-how-to-achieve-a-high-degree-of-adaptive.html

 

今天須要些一個回覆評論的頁面，設計師給的初始界面就是一個只有一行的框。而後當時就想這個交互該怎麼實現比較好，而後想起了新浪微博的作法：點擊評論，默認顯示一行，當輸入的文字超過一行或者輸入Enter時，輸入框的高度會隨着改變，直到輸入完畢。頓時以爲這個細節作得挺不錯的，能夠效仿下。下面分享2種實現textarea高度自適應的作法，一種是用div來模擬textarea來實現的，用CSS控制樣式，不用JS；另外一種是利用JS控制的（由於存在瀏覽器兼容問題，因此寫起來比較麻煩）；

方法一：div模擬textarea文本域輕鬆實現高度自適應

demo演示地址：http://www.xuanfengge.com/demo/201308/textarea/demo1.html

由於textarea不支持自適應高度，就是定好高度或者是行數以後，超出部分就會顯示滾動條，看起來不美觀。

而用DIV來模擬時，首先遇到的問題是：div怎麼實現輸入功能？

可能咱們仍是第一次見到這個屬性contenteditable，如一個普通的block元素上加個contenteditable="true"就實現編輯，出現光標了。如

 

1	<div contenteditable="true"></div>

contenteditable屬性雖是HTML5裏面的內容，可是IE彷佛老早就支持此標籤屬性了。因此，兼容性方面仍是不用太擔憂的。

CSS代碼

 

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.textarea{     width: 400px;     min-height: 20px;     max-height: 300px;     _height: 120px;     margin-left: auto;     margin-right: auto;     padding: 3px;     outline: 0;     border: 1px solid #a0b3d6;     font-size: 12px;     line-height: 24px;     padding: 2px;     word-wrap: break-word;     overflow-x: hidden;     overflow-y: auto;       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); }

 HTML代碼

 

1	<div class="textarea" contenteditable="true"><br /></div>

CSS代碼中，由於IE6不支持min/max，因此作了hack，其餘的也好理解。

 

方法二：文本框textarea根據輸入內容自適應高度

demo演示地址:http://www.xuanfengge.com/demo/201308/textarea/demo2.html

這個寫法是用原生JS寫的，考慮了不少兼容性問題，徹底和新浪微博的回覆效果同樣的功能。有興趣的童鞋能夠仔細分析下代碼。

CSS代碼

 

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#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); }

JavaScript代碼

 

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/** * 文本框根據輸入內容自適應高度 * @param                {HTMLElement}        輸入框元素 * @param                {Number}                設置光標與輸入框保持的距離(默認0) * @param                {Number}                設置最大高度(可選) */ 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代碼（寫在body裏面的）

 

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<textarea id="textarea" placeholder="回覆內容"></textarea>     <script>         var text = document.getElementById("textarea");         autoTextarea(text);// 調用     </script>

 

 其餘方法

• A different approach to elastic textareas
• Build an Elastic Textarea with Ext JS
• Smart TextArea: scrollHeight in IE, Firefox, Opera and Safari