feat: add dateFormatString function (#12)

* feat: add dateFormatString function, that returns full raw format depending on actual date date

Author: Vasil Raev

src/dates.d.ts

@@ -19,3 +19,4 @@ export function formatDate(value: Date, format: String|DateFormatOptions, locale
 
 export function parseDate(value: string, format?: String|DateFormatOptions|Array<String>|Array<DateFormatOptions>, locale?: string): Date;
 
+export function dateFormatString(value: Date, format: String|DateFormatOptions, locale?: string): string;

src/dates.js

@@ -1,2 +1,3 @@
 export { default as formatDate } from './dates/format-date';
-export { default as parseDate } from './dates/parse-date';
+export { default as parseDate } from './dates/parse-date';
+export { default as dateFormatString } from './dates/date-format-string';

src/dates/date-format-string.js

@@ -0,0 +1,5 @@
+import dateGenericFormat from './date-generic-format';
+
+export default function dateFormatString(date, format, locale = "en") {
+    return dateGenericFormat(date, format, locale, true);
+}

src/dates/date-generic-format.js

@@ -0,0 +1,206 @@
+import { localeInfo, firstDay } from '../cldr';
+import formatString from '../common/format-string';
+import datePattern from './date-pattern';
+import formatNames from './format-names';
+import pad from '../common/pad';
+import isDate from '../common/is-date';
+
+const dateFormatRegExp = /d{1,2}|E{1,6}|e{1,6}|c{3,6}|c{1}|M{1,5}|L{1,5}|y{1,4}|H{1,2}|h{1,2}|m{1,2}|a{1,5}|s{1,2}|S{1,3}|z{1,4}|Z{1,5}|x{1,5}|X{1,5}|G{1,5}|q{1,5}|Q{1,5}|"[^"]*"|'[^']*'/g;
+
+function formatDayOfWeekIndex(day, formatLength, localeInfo) {
+    const firstDayIndex = firstDay(localeInfo);
+    let dayIndex;
+    if (day < firstDayIndex) {
+        dayIndex = 7 - firstDayIndex + day;
+    } else {
+        dayIndex = day - firstDayIndex;
+    }
+
+    return dayIndex + 1;
+}
+
+function formatMonth(month, formatLength, info, standAlone) {
+    if (formatLength <= 2) {
+        return pad(month + 1, formatLength);
+    }
+    return formatNames(info, "months", formatLength, standAlone)[month];
+}
+
+function formatQuarter(date, formatLength, info, standAlone) {
+    const quarter = Math.floor(date.getMonth() / 3);
+    if (formatLength < 3) {
+        return quarter + 1;
+    }
+
+    return formatNames(info, "quarters", formatLength, standAlone)[quarter];
+}
+
+
+function formatTimeZone(date, info, options) {
+    const { shortHours, optionalMinutes, separator, localizedName, zZeroOffset } = options;
+    const offset = date.getTimezoneOffset() / 60;
+    if (offset === 0 && zZeroOffset) {
+        return "Z";
+    }
+    const sign = offset <= 0 ? "+" : "-";
+    const hoursMinutes = Math.abs(offset).toString().split(".");
+    const minutes = hoursMinutes[1] || 0;
+    let result = sign + (shortHours ? hoursMinutes[0] : pad(hoursMinutes[0], 2));
+    if (minutes || !optionalMinutes) {
+        result += (separator ? ":" : "") + pad(minutes, 2);
+    }
+
+    if (localizedName) {
+        const localizedFormat = offset === 0 ? info.calendar.gmtZeroFormat : info.calendar.gmtFormat;
+        result = formatString(localizedFormat, result);
+    }
+
+    return result;
+}
+function formatDayOfWeek(date, formatLength, info, standAlone) {
+    let result;
+    if (formatLength < 3) {
+        result = formatDayOfWeekIndex(date.getDay(), formatLength, info);
+    } else {
+        result = formatNames(info, "days", formatLength, standAlone)[date.getDay()];
+    }
+    return result;
+}
+
+
+const formatters = {};
+
+formatters.d = function(date, formatLength) {
+    return pad(date.getDate(), formatLength);
+};
+
+formatters.E = function(date, formatLength, info) {
+    return formatNames(info, "days", formatLength)[date.getDay()];
+};
+
+formatters.M = function(date, formatLength, info) {
+    return formatMonth(date.getMonth(), formatLength, info, false);
+};
+
+formatters.L = function(date, formatLength, info) {
+    return formatMonth(date.getMonth(), formatLength, info, true);
+};
+
+formatters.y = function(date, formatLength) {
+    let year = date.getFullYear();
+    if (formatLength === 2) {
+        year = year % 100;
+    }
+    return pad(year, formatLength);
+};
+
+formatters.h = function(date, formatLength) {
+    const hours = date.getHours() % 12 || 12;
+    return pad(hours, formatLength);
+};
+
+formatters.H = function(date, formatLength) {
+    return pad(date.getHours(), formatLength);
+};
+
+formatters.m = function(date, formatLength) {
+    return pad(date.getMinutes(), formatLength);
+};
+
+formatters.s = function(date, formatLength) {
+    return pad(date.getSeconds(), formatLength);
+};
+
+formatters.S = function(date, formatLength) {
+    const milliseconds = date.getMilliseconds();
+    let result;
+    if (milliseconds !== 0) {
+        result = String(date.getMilliseconds() / 1000).split(".")[1].substr(0, formatLength);
+    } else {
+        result = pad("", formatLength);
+    }
+    return result;
+};
+
+formatters.a = function(date, formatLength, info) {
+    return formatNames(info, "dayPeriods", formatLength)[date.getHours() < 12 ? "am" : "pm"];
+};
+
+formatters.z = function(date, formatLength, info) {
+    return formatTimeZone(date, info, {
+        shortHours: formatLength < 4,
+        optionalMinutes: formatLength < 4,
+        separator: true,
+        localizedName: true
+    });
+};
+
+formatters.Z = function(date, formatLength, info) {
+    return formatTimeZone(date, info, {
+        separator: formatLength > 3,
+        localizedName: formatLength === 4,
+        zZeroOffset: formatLength === 5
+    });
+};
+
+formatters.x = function(date, formatLength, info) {
+    return formatTimeZone(date, info, {
+        optionalMinutes: formatLength === 1,
+        separator: formatLength === 3 || formatLength === 5
+    });
+};
+
+formatters.X = function(date, formatLength, info) {
+    return formatTimeZone(date, info, {
+        optionalMinutes: formatLength === 1,
+        separator: formatLength === 3 || formatLength === 5,
+        zZeroOffset: true
+    });
+};
+
+formatters.G = function(date, formatLength, info) {
+    let era = date.getFullYear() >= 0 ? 1 : 0;
+    return formatNames(info, "eras", formatLength)[era];
+};
+
+formatters.e = formatDayOfWeek;
+
+formatters.c = function(date, formatLength, info) {
+    return formatDayOfWeek(date, formatLength, info, true);
+};
+
+formatters.q = function(date, formatLength, info) {
+    return formatQuarter(date, formatLength, info, true);
+};
+
+formatters.Q = formatQuarter;
+
+export default function dateGenericFormat(date, format, locale = "en", returnPattern = false) {
+    if (!isDate(date)) {
+        return returnPattern ? format : date;
+    }
+
+    const info = localeInfo(locale);
+    const pattern = datePattern(format, info);
+
+    return pattern.replace(dateFormatRegExp, function(match) {
+        let formatLength = match.length;
+        let result;
+
+        if (match.includes("'") || match.includes("\"")) {
+            result = match.slice(1, formatLength - 1);
+        } else {
+            result = formatters[match[0]](date, formatLength, info);
+
+            if (returnPattern) {
+                let length = (result || "").toString().length;
+                result = "";
+                while (length > 0) {
+                    result += match[0];
+                    length--;
+                }
+            }
+        }
+        return result;
+    });
+}