mastodon_neko/app/javascript/mastodon/locales/locale-data/README.md

Custom Locale Data

This folder is used to store custom locale data. These custom locale data are not yet provided by Unicode Common Locale Data Repository and hence not provided in react-intl/locale-data/*.

The locale data should support Locale Data APIs of the react-intl library.

It is recommended to start your custom locale data from this sample English locale data (*):

/*eslint eqeqeq: "off"*/
/*eslint no-nested-ternary: "off"*/

export default [
  {
    locale: "en",
    pluralRuleFunction: function(e, a) {
      var n = String(e).split("."),
        l = !n[1],
        o = Number(n[0]) == e,
        t = o && n[0].slice(-1),
        r = o && n[0].slice(-2);
      return a ? 1 == t && 11 != r ? "one" : 2 == t && 12 != r ? "two" : 3 == t && 13 != r ? "few" : "other" : 1 == e && l ? "one" : "other"
    },
    fields: {
      year: {
        displayName: "year",
        relative: {
          0: "this year",
          1: "next year",
          "-1": "last year"
        },
        relativeTime: {
          future: {
            one: "in {0} year",
            other: "in {0} years"
          },
          past: {
            one: "{0} year ago",
            other: "{0} years ago"
          }
        }
      },
      month: {
        displayName: "month",
        relative: {
          0: "this month",
          1: "next month",
          "-1": "last month"
        },
        relativeTime: {
          future: {
            one: "in {0} month",
            other: "in {0} months"
          },
          past: {
            one: "{0} month ago",
            other: "{0} months ago"
          }
        }
      },
      day: {
        displayName: "day",
        relative: {
          0: "today",
          1: "tomorrow",
          "-1": "yesterday"
        },
        relativeTime: {
          future: {
            one: "in {0} day",
            other: "in {0} days"
          },
          past: {
            one: "{0} day ago",
            other: "{0} days ago"
          }
        }
      },
      hour: {
        displayName: "hour",
        relativeTime: {
          future: {
            one: "in {0} hour",
            other: "in {0} hours"
          },
          past: {
            one: "{0} hour ago",
            other: "{0} hours ago"
          }
        }
      },
      minute: {
        displayName: "minute",
        relativeTime: {
          future: {
            one: "in {0} minute",
            other: "in {0} minutes"
          },
          past: {
            one: "{0} minute ago",
            other: "{0} minutes ago"
          }
        }
      },
      second: {
        displayName: "second",
        relative: {
          0: "now"
        },
        relativeTime: {
          future: {
            one: "in {0} second",
            other: "in {0} seconds"
          },
          past: {
            one: "{0} second ago",
            other: "{0} seconds ago"
          }
        }
      }
    }
  }
]

Notes

Plural Rules

The function pluralRuleFunction() should return the key to proper string of a plural form(s). The purpose of the function is to provide key of translate strings of correct plural form according. The different forms are described in CLDR's Plural Rules,

Quick Overview on CLDR Rules

Let's take English as an example.

When you describe a number, you can be either describe it as:

• Cardinals: 1st, 2nd, 3rd ... 11th, 12th ... 21st, 22nd, 23nd ....
• Ordinals: 1, 2, 3 ...

In any of these cases, the nouns will reflect the number with singular or plural form. For example:

• in 0 days
• in 1 day
• in 2 days

The pluralRuleFunction receives 2 parameters:

• e: a string representation of the number. Such as, "1", "2", "2.1".
• a: true if this is "cardinal" type of description. false for ordinal and other case.

How you should write pluralRuleFunction

The first rule to write pluralRuleFunction is never translate the output string into your language. Plural Rules specified you should use these as the return values:

• "zero"
• "one" (singular)
• "two" (dual)
• "few" (paucal)
• "many" (also used for fractions if they have a separate class)
• "other" (required—general plural form—also used if the language only has a single form)

Again, we'll use English as the example here.

Let's read the return statement in the pluralRuleFunction above:

  return a ? 1 == t && 11 != r ? "one" : 2 == t && 12 != r ? "two" : 3 == t && 13 != r ? "few" : "other" : 1 == e && l ? "one" : "other"

This nested ternary is hard to read. It basically means:

// e: the number variable to examine
// a: "true" if cardinals
// l: "true" if the variable e has nothin after decimal mark (e.g. "1.0" would be false)
// o: "true" if the variable e is an integer
// t: the "ones" of the number. e.g. "3" for number "9123"
// r: the "ones" and "tens" of the number. e.g. "23" for number "9123"
if (a == true) {
  if (t == 1 && r != 11) {
    return "one"; // i.e. 1st, 21st, 101st, 121st ...
  } else if (t == 2 && r != 12) {
    return "two"; // i.e. 2nd, 22nd, 102nd, 122nd ...
  } else if (t == 3 && r != 13) {
    return "few"; // i.e. 3rd, 23rd, 103rd, 123rd ...
  } else {
    return "other"; // i.e. 4th, 11th, 12th, 24th ...
  }
} else {
  if (e == 1 && l) {
    return "one"; // i.e. 1 day
  } else {
    return "other"; // i.e. 0 days, 2 days, 3 days
  }
}

If your language, like French, do not have complicated cardinal rules, you may use the French's version of it:

function (e, a) {
  return a ? 1 == e ? "one" : "other" : e >= 0 && e < 2 ? "one" : "other";
}

If your language, like Chinese, do not have any pluralization rule at all you may use the Chinese's version of it:

function (e, a) {
  return "other";
}