The Intl.DateTimeFormat object is a constructor for objects that enable language and locale specific date and time formatting.

On May 1, 2019, the imperial year should be changed to 令和元年, if the new era name is implemented in your browser!!!

Updated on April 30, 2019 (6pm in PDT):
It is already a new Reiwa era in JST, but I don't see this implemented on major browsers yet. Only browser I see this in effect is the latest Chrome Canary.

      
const jpDate = new Intl.DateTimeFormat(
  'ja-JP-u-ca-japanese', {era: 'long'}
);

jpDate.format(Date.now());
      
      

and it should return: