基本信息
源码名称：javascript 文本框自适应高度实例 附源码
源码大小：2.11KB
文件格式：.zip
开发语言：js
更新时间：2013-03-27
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   源码介绍

根据用户输入的内容 textbox自适应高度，兼容IE6以及以上版本


js:

  

/**
 * 文本框根据输入内容自适应高度
 * @author		tang bin
 * @version		0.3
 * @see			http://www.planeart.cn/?p=1489
 * @param		{HTMLElement}	输入框元素
 * @param		{Number}		设置光标与输入框保持的距离(默认20)
 * @param		{Number}		设置最大高度(可选)
 */
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();
};


  

<!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>