html：

<p contenteditable="true" class="test_box"></p>

js的封装：

//自适应高度 /** * 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(); };

调用js的封装

// 自定义textarea的高度 var text = document.getElementById("textarea"); autoTextarea(text);

css:

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