js把字符串(yyyymmdd)轉換成日期格式（yyyy-mm-dd）

1、第一種寫法：

var r="20112233".replace(/^(\d{4})(\d{2})(\d{2})$/, "$1-$2-$3")

2、第二種寫法：　

var dateString = '19930701';
var pattern = /(\d{4})(\d{2})(\d{2})/;
var formatedDate = dateString.replace(pattern, '$1-$2-$3');