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      JS Intl.DateTimeFormat formatToParts()

      The Intl.DateTimeFormat.prototype.formatToParts() method allows locale-aware formatting of strings produced by DateTimeFormat formatters.

      Syntax

      dateTimeFormat.formatToParts(date)
      

      Parameters

      date Optional

      The date to format.

      Return value

      An Array of objects containing the formatted date in parts.

      Description

      The formatToParts() method is useful for custom formatting of date strings. It returns an Array of objects containing the locale-specific tokens from which it possible to build custom strings while preserving the locale-specific parts. The structure the formatToParts() method returns, looks like this:

      [
        { type: 'day', value: '17' },
        { type: 'weekday', value: 'Monday' }
      ]
      

      Possible types are the following:

      day

      The string used for the day, for example "17".

      dayPeriod

      The string used for the day period, for example, "AM" or "PM".

      era

      The string used for the era, for example "BC" or "AD".

      hour

      The string used for the hour, for example "3" or "03".

      literal

      The string used for separating date and time values, for example "/", ",", "o'clock", "de", etc.

      minute

      The string used for the minute, for example "00".

      month

      The string used for the month, for example "12".

      second

      The string used for the second, for example "07" or "42".

      timeZoneName

      The string used for the name of the time zone, for example "UTC".

      weekday

      The string used for the weekday, for example "M", "Monday", or "Montag".

      year

      The string used for the year, for example "2012" or "96".

      Examples

      DateTimeFormat outputs localized, opaque strings that cannot be manipulated directly:

      var date = Date.UTC(2012, 11, 17, 3, 0, 42);
      
      var formatter = new Intl.DateTimeFormat('en-us', {
        weekday: 'long',
        year: 'numeric',
        month: 'numeric',
        day: 'numeric',
        hour: 'numeric',
        minute: 'numeric',
        second: 'numeric',
        hour12: true,
        timeZone: 'UTC'
      });
      
      formatter.format(date);
      // "Monday, 12/17/2012, 3:00:42 AM"
      
      

      However, in many User Interfaces there is a desire to customize the formatting of this string. The formatToParts method enables locale-aware formatting of strings produced by DateTimeFormat formatters by providing you the string in parts:

      formatter.formatToParts(date);
      
      // return value: 
      [ 
        { type: 'weekday',   value: 'Monday' }, 
        { type: 'literal',   value: ', '     }, 
        { type: 'month',     value: '12'     }, 
        { type: 'literal',   value: '/'      }, 
        { type: 'day',       value: '17'     }, 
        { type: 'literal',   value: '/'      }, 
        { type: 'year',      value: '2012'   }, 
        { type: 'literal',   value: ', '     }, 
        { type: 'hour',      value: '3'      }, 
        { type: 'literal',   value: ':'      }, 
        { type: 'minute',    value: '00'     }, 
        { type: 'literal',   value: ':'      }, 
        { type: 'second',    value: '42'     }, 
        { type: 'literal',   value: ' '      }, 
        { type: 'dayPeriod', value: 'AM'     } 
      ]
      
      

      Now the information is available separately and it can be formatted and concatenated again in a customized way. For example by using Array.prototype.map(), [arrow functions], a [switch statement], template literals, and Array.prototype.reduce().

      var dateString = formatter.formatToParts(date).map(({type, value}) => { 
        switch (type) {
          case 'dayPeriod': return `${value}`; 
          default : return value; 
        } 
      }).reduce((string, part) => string + part);
      
      

      This will make the day period bold, when using the formatToParts() method.

      console.log(formatter.format(date));
      // "Monday, 12/17/2012, 3:00:42 AM"
      
      console.log(dateString);
      // "Monday, 12/17/2012, 3:00:42 AM"
      

      Polyfill

      A polyfill for this feature is available in the proposal repository.

      Specifications

      SpecificationStatusComment
      [ECMAScript Internationalization API 4.0 (ECMA-402)
      The definition of ‘Intl.DateTimeFormat.prototype.formatToParts’ in that specification.](https://tc39.es/ecma402/#sec-Intl.DateTimeFormat.prototype.formatToParts)DraftInitial definition

      See also

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