JS，如何将没有分隔符的字符串格式化为日期

Question

So I have a date that I get from an external custom api, that comes in as plain string format with no delimiters.

How would I format it into a date.

String -> Date

20090506 -> 2009-05-06

I have browsed around stack overflow for a solution but it seems like all the answers revolve around a string with delimiters in between.

Answer 1

Basic regular expression with replace.

 function alterFormat(ds) { return ds.toString().replace(/(\d{4})(\d{2})(\d{2})/, '$1-$2-$3'); } console.log(alterFormat(20200220)); console.log(alterFormat(20190220)); console.log(alterFormat(20201012));

Answer 2

You can use substring() to extract the year, month, and day, then you can use new Date() to convert it into a Date object.

 var date = "20090506"; var formattedDate = `${date.substring(0, 4)}-${date.substring(4, 6)}-${date.substring(6, 8)}`; console.log(formattedDate); console.log(new Date(formattedDate));