textarea实现宽度不变高度自适应
代码非原创。原文链接/wangjae/p/11150128.html
演示地址：https://xibushijie.github.io/static/textareaHeihgAuto.html
此textarea非彼textarea ，有经验的老司机们应该知道html标签contenteditable这个属性。利用此属性使当前的标签成为可以输入的状态，等同于输入框。<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta http-equiv="X-UA-Compatible" content="ie=edge"><title>textarea输入内容</title><style>#textarea {width: 100px;margin: 0 auto;min-height: 20px;max-height: 100%;outline: 0;border: 1px solid #397EFF;font-size: 13px;overflow-x: hidden;overflow-y: auto;-webkit-user-modify: read-write-plaintext-only;}[contentEditable=true]:empty:not(:focus):before {content: attr(data-text);}</style></head><body><div id="textarea" contenteditable="true" data-text="输入内容..."></div></body></html>
