Convert Date from one format to another format in JavaScript

Question

I have a string of a date in javascript in format #1. I need to convert it to format #2.

The problem starts when one format is "dd/mm/yy" and the other is "mm/dd/yy".

The formats change dynamically and I have the formats as strings, but I need a function like

   Date newDate = convert(currentDate, currentFormatString, newFormatString).

How can I do it?

Answer 1

You should look into momentjs, which is a javascript date/time library. With that, you can easily convert between dates of different format. In your case, it would be:

string newDate = moment(currentDate, currentFormatString).format(newFormatString)

For example, moment("21/10/14", "DD/MM/YY").format("MM/DD/YY") would return "10/21/14"

Answer 2

You can use the function below

console.log(changeDateFormat('12/1/2020','dd/MM/yyyy','MM/dd/yyyy'));

function changeDateFormat(value, inputFormat, outputFormat) {

let outputSplitter = "/";
let strOutputFormat = outputFormat.split(outputSplitter).map(i => i.toUpperCase());
if (strOutputFormat.length != 3) {
  strOutputFormat = outputFormat.split('-');
  outputSplitter = '-';
}

if (strOutputFormat.length != 3) throw new Error('wrong output format splitter :(');

let date = null;

if (value instanceof Date) {
  date = {
    ["YYYY"]: value.getUTCFullYear(),
    ["MM"]: value.getMonth() + 1,
    ["DD"]: value.getDate()
  }
}

if (typeof value == 'string') {
  let inputSplitter = "/";

  var strInputFormat = inputFormat.split(inputSplitter).map(i => i.toUpperCase());
  if (strInputFormat.length != 3) {
    strInputFormat = inputFormat.split('-');
    inputSplitter = '-';
  }

  if (strInputFormat.length != 3) throw new Error('wrong input format splitter :(');

  let dateElements = value.split(inputSplitter);
  if (dateElements.length != 3) throw new Error('wrong value :(');

  date = {
    [strInputFormat[0]]: dateElements[0],
    [strInputFormat[1]]: dateElements[1],
    [strInputFormat[2]]: dateElements[2],
  }
}

if (!date) throw new Error('unsupported value type:(');

let result = date[strOutputFormat[0]] + outputSplitter
  + date[strOutputFormat[1]] + outputSplitter 
  + date[strOutputFormat[2]];

return result;
 }