1、第一种写法：
var r="20112233".replace(/^(\d{4})(\d{2})(\d{2})$/, "$1-$2-$3")2、第二种写法：
var dateString = ‘19930701‘;var pattern = /(\d{4})(\d{2})(\d{2})/;var formatedDate = dateString.replace(pattern, ‘$1-$2-$3‘);
js把字符串(yyyymmdd)转换成日期格式（yyyy-mm-dd）
原文地址：https://www.cnblogs.com/mentiantian/p/10333804.html