Native method to inverse Date.toLocaleString convertion in JavaScript?

Question

We have date converted to locale string. For example:

x = (new Date()).toLocaleString()

and x has value

"20.05.2018, 10:21:37"

How to process this string to Date object.

I was tried

new Date(x)
Invalid Date

and

Date.parse(x)
NaN

It is possible and simple to do without external libraries like moment.js?

[Why does parsing a locale date string result in an invalid date?](https://stackoverflow.com/questions/29988868/why-does-parsing-a-locale-date-string-result-in-an-invalid-date) — deEr., May 20 '18 at 08:38
You don't need to parse again the stringified date, just store date in a variable `date`and use it: `date = new Date(); dateStr = date.toLocaleString();` — Alejandro Blasco, May 20 '18 at 08:41

Matus Dubrava · Accepted Answer · 2018-05-20T09:39:27.253

4

You can parse it on your own.

const date = "20.05.2018, 10:21:37";
const [first, second] = date.split(',').map(item => item.trim());
const [day, month, year] = first.split('.');
const [hours, minutes, seconds] = second.split(':');

const newDate = new Date(year, month - 1, day, hours, minutes, seconds);
console.log(newDate);

Or using regex

const date = "20.05.2018, 10:21:37";
const m = /^(\d{2})\.(\d{2})\.(\d{4}), (\d{2}):(\d{2}):(\d{2})$/.exec(date);
const newDate = new Date(m[3], m[2] - 1, m[1], m[4], m[5], m[6]);
console.log(newDate);

edited May 20 '18 at 09:39

answered May 20 '18 at 08:40

Matus Dubrava

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The split can be simplified using `dateString.split(/\D+/)` to get all the numeric values in one go, so `let [d,m,y,h,M,s] = "20.05.2018, 10:21:37".split(/\D+/); new Date(y,m-1,d,h,M,s)`. ;-) – RobG May 20 '18 at 21:44

score 2 · Answer 2 · answered May 20 '18 at 10:09

It is possible to use Intl.DateTimeFormat.prototype.formatToParts() to get the format of the date without knowing it beforehand.

// should default to toLocaleDateString() format
var formatter = Intl.DateTimeFormat()
// I suggest formatting the timestamp used in
// Go date formatting functions to be able to 
// extract the full scope of format rules
var dateFormat = formatter.formatToParts(new Date(1136239445999))

On my machine dateFormat yields

[
    {type: "month", value: "1"},
    {type: "literal", value: "/"},
    {type: "day", value: "3"},
    {type: "literal", value: "/"},
    {type: "year", value: "2006"},
]

By iterating over this array it should be feasible to parse a string into parts and then fill them in a Date object.

Native method to inverse Date.toLocaleString convertion in JavaScript?

2 Answers2