js把字符串(yyyymmdd)转换成日期格式（yyyy-mm-dd）

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

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

function formatStringyyyyMMddToyyyy_MM_dd (value){
if(value.length == 8){
return value.substring(0, 4) + "-" + value.substring(4, 6) + "-" + value.substring(6, 8);
} else if(value.length == 6){
return value.substring(0, 4) + "-" + value.substring(4, 6);
} else {
return value;
}
}