使textarea可以达到具有默认提示文字，且当用户输入文字时提示文字自动删除，并且由提示文字的字体颜色浅灰色变为正常的输入文字黑色，可通过js实现。
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="maximum-scale=1.0,minimum-scale=1.0,user-scalable=0,width=device-width,initial-scale=1.0"/>
<meta name="format-detection" content="telephone=no,email=no,date=no,address=no">
<title>title</title>
<style>
#textarea{
overflow:hidden;
margin-top:2rem;
margin-left:0.5rem;
height:10rem;
width:95%;
outline: none;
border:0;
background:#f9f9f9;
}
</style>
</head>
<body>
<textarea id="textarea" placeholder="添加作品描述，如：塔米APP的iOS主开发工程师，负责整体架构设计..."></textarea>
</body>
<script type="text/javascript" src="../script/api.js"></script>
<script type="text/javascript">
apiready = function(){
};
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();
};
</script>
<script type="text/javascript">
var text=document.getElementById("textarea");
autoTextarea(text);//调用
</script>
</html>
</html>
