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‘);