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textarea自适应高度

2013-07-31 12:09 211 查看
 
<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml" >

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

<title>文本框根据输入内容自适应高度</title>

<style type="text/css">

#textarea { font: 1.4em/1.8em Arial; overflow: hidden; width: 550px; height: 6em; padding:10px; }

</style>

<script src="autoTextarea.js"></script>

</head>

<body style="background:#FBFCFD url(http://goo.gl/kLsZX);">

<textarea id="textarea"></textarea>

<script>

var text = document.getElementById("textarea"),

tip = '想写点什么..';

autoTextarea(text);// 调用

text.value = tip;

text.onfocus = function () {

if (text.value === tip) text.value = '';

};

text.onblur = function () {

if (text.value === '') text.value = tip;

};

</script>

</body>

</html>
var autoTextarea = function (elem, extra, maxHeight) {extra = extra || 20;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.maxHeight = 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();};
 
                                            

                                        

                        
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