JS - 控制 textarea 根据内容自适应高度

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本文来自同事代码，以此记录，如有相同，请收下在下的膝盖。

<script>
	
	// 页面加载调用
	ableMutibleTextArea();
	function ableMutibleTextArea(){
    
    
		$('textarea').each(function(value,ele)
		{
    
    
			autoTextarea(ele);
		});
	}

	/**
	 * 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';
	            };
	            height = height * 1 + 10;
	            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();
	};
</script>