<form method="POST">
    <h3>Editing: month.js</h3>
    <textarea name="content" rows="20" cols="80">import { get } from '../moment/get-set';
import hasOwnProp from '../utils/has-own-prop';
import { addFormatToken } from '../format/format';
import { addUnitAlias } from './aliases';
import { addRegexToken, match1to2, match2, matchWord, regexEscape } from '../parse/regex';
import { addParseToken } from '../parse/token';
import { hooks } from '../utils/hooks';
import { MONTH } from './constants';
import toInt from '../utils/to-int';
import isArray from '../utils/is-array';
import indexOf from '../utils/index-of';
import { createUTC } from '../create/utc';
import getParsingFlags from '../create/parsing-flags';

export function daysInMonth(year, month) {
    return new Date(Date.UTC(year, month + 1, 0)).getUTCDate();
}

// FORMATTING

addFormatToken('M', ['MM', 2], 'Mo', function () {
    return this.month() + 1;
});

addFormatToken('MMM', 0, 0, function (format) {
    return this.localeData().monthsShort(this, format);
});

addFormatToken('MMMM', 0, 0, function (format) {
    return this.localeData().months(this, format);
});

// ALIASES

addUnitAlias('month', 'M');

// PARSING

addRegexToken('M',    match1to2);
addRegexToken('MM',   match1to2, match2);
addRegexToken('MMM',  function (isStrict, locale) {
    return locale.monthsShortRegex(isStrict);
});
addRegexToken('MMMM', function (isStrict, locale) {
    return locale.monthsRegex(isStrict);
});

addParseToken(['M', 'MM'], function (input, array) {
    array[MONTH] = toInt(input) - 1;
});

addParseToken(['MMM', 'MMMM'], function (input, array, config, token) {
    var month = config._locale.monthsParse(input, token, config._strict);
    // if we didn't find a month name, mark the date as invalid.
    if (month != null) {
        array[MONTH] = month;
    } else {
        getParsingFlags(config).invalidMonth = input;
    }
});

// LOCALES

var MONTHS_IN_FORMAT = /D[oD]?(\[[^\[\]]*\]|\s+)+MMMM?/;
export var defaultLocaleMonths = 'January_February_March_April_May_June_July_August_September_October_November_December'.split('_');
export function localeMonths (m, format) {
    return isArray(this._months) ? this._months[m.month()] :
        this._months[MONTHS_IN_FORMAT.test(format) ? 'format' : 'standalone'][m.month()];
}

export var defaultLocaleMonthsShort = 'Jan_Feb_Mar_Apr_May_Jun_Jul_Aug_Sep_Oct_Nov_Dec'.split('_');
export function localeMonthsShort (m, format) {
    return isArray(this._monthsShort) ? this._monthsShort[m.month()] :
        this._monthsShort[MONTHS_IN_FORMAT.test(format) ? 'format' : 'standalone'][m.month()];
}

function handleStrictParse(monthName, format, strict) {
    var i, ii, mom, llc = monthName.toLocaleLowerCase();
    if (!this._monthsParse) {
        // this is not used
        this._monthsParse = [];
        this._longMonthsParse = [];
        this._shortMonthsParse = [];
        for (i = 0; i &lt; 12; ++i) {
            mom = createUTC([2000, i]);
            this._shortMonthsParse[i] = this.monthsShort(mom, '').toLocaleLowerCase();
            this._longMonthsParse[i] = this.months(mom, '').toLocaleLowerCase();
        }
    }

    if (strict) {
        if (format === 'MMM') {
            ii = indexOf.call(this._shortMonthsParse, llc);
            return ii !== -1 ? ii : null;
        } else {
            ii = indexOf.call(this._longMonthsParse, llc);
            return ii !== -1 ? ii : null;
        }
    } else {
        if (format === 'MMM') {
            ii = indexOf.call(this._shortMonthsParse, llc);
            if (ii !== -1) {
                return ii;
            }
            ii = indexOf.call(this._longMonthsParse, llc);
            return ii !== -1 ? ii : null;
        } else {
            ii = indexOf.call(this._longMonthsParse, llc);
            if (ii !== -1) {
                return ii;
            }
            ii = indexOf.call(this._shortMonthsParse, llc);
            return ii !== -1 ? ii : null;
        }
    }
}

export function localeMonthsParse (monthName, format, strict) {
    var i, mom, regex;

    if (this._monthsParseExact) {
        return handleStrictParse.call(this, monthName, format, strict);
    }

    if (!this._monthsParse) {
        this._monthsParse = [];
        this._longMonthsParse = [];
        this._shortMonthsParse = [];
    }

    // TODO: add sorting
    // Sorting makes sure if one month (or abbr) is a prefix of another
    // see sorting in computeMonthsParse
    for (i = 0; i &lt; 12; i++) {
        // make the regex if we don't have it already
        mom = createUTC([2000, i]);
        if (strict &amp;&amp; !this._longMonthsParse[i]) {
            this._longMonthsParse[i] = new RegExp('^' + this.months(mom, '').replace('.', '') + '$', 'i');
            this._shortMonthsParse[i] = new RegExp('^' + this.monthsShort(mom, '').replace('.', '') + '$', 'i');
        }
        if (!strict &amp;&amp; !this._monthsParse[i]) {
            regex = '^' + this.months(mom, '') + '|^' + this.monthsShort(mom, '');
            this._monthsParse[i] = new RegExp(regex.replace('.', ''), 'i');
        }
        // test the regex
        if (strict &amp;&amp; format === 'MMMM' &amp;&amp; this._longMonthsParse[i].test(monthName)) {
            return i;
        } else if (strict &amp;&amp; format === 'MMM' &amp;&amp; this._shortMonthsParse[i].test(monthName)) {
            return i;
        } else if (!strict &amp;&amp; this._monthsParse[i].test(monthName)) {
            return i;
        }
    }
}

// MOMENTS

export function setMonth (mom, value) {
    var dayOfMonth;

    if (!mom.isValid()) {
        // No op
        return mom;
    }

    if (typeof value === 'string') {
        if (/^\d+$/.test(value)) {
            value = toInt(value);
        } else {
            value = mom.localeData().monthsParse(value);
            // TODO: Another silent failure?
            if (typeof value !== 'number') {
                return mom;
            }
        }
    }

    dayOfMonth = Math.min(mom.date(), daysInMonth(mom.year(), value));
    mom._d['set' + (mom._isUTC ? 'UTC' : '') + 'Month'](value, dayOfMonth);
    return mom;
}

export function getSetMonth (value) {
    if (value != null) {
        setMonth(this, value);
        hooks.updateOffset(this, true);
        return this;
    } else {
        return get(this, 'Month');
    }
}

export function getDaysInMonth () {
    return daysInMonth(this.year(), this.month());
}

export var defaultMonthsShortRegex = matchWord;
export function monthsShortRegex (isStrict) {
    if (this._monthsParseExact) {
        if (!hasOwnProp(this, '_monthsRegex')) {
            computeMonthsParse.call(this);
        }
        if (isStrict) {
            return this._monthsShortStrictRegex;
        } else {
            return this._monthsShortRegex;
        }
    } else {
        return this._monthsShortStrictRegex &amp;&amp; isStrict ?
            this._monthsShortStrictRegex : this._monthsShortRegex;
    }
}

export var defaultMonthsRegex = matchWord;
export function monthsRegex (isStrict) {
    if (this._monthsParseExact) {
        if (!hasOwnProp(this, '_monthsRegex')) {
            computeMonthsParse.call(this);
        }
        if (isStrict) {
            return this._monthsStrictRegex;
        } else {
            return this._monthsRegex;
        }
    } else {
        return this._monthsStrictRegex &amp;&amp; isStrict ?
            this._monthsStrictRegex : this._monthsRegex;
    }
}

function computeMonthsParse () {
    function cmpLenRev(a, b) {
        return b.length - a.length;
    }

    var shortPieces = [], longPieces = [], mixedPieces = [],
        i, mom;
    for (i = 0; i &lt; 12; i++) {
        // make the regex if we don't have it already
        mom = createUTC([2000, i]);
        shortPieces.push(this.monthsShort(mom, ''));
        longPieces.push(this.months(mom, ''));
        mixedPieces.push(this.months(mom, ''));
        mixedPieces.push(this.monthsShort(mom, ''));
    }
    // Sorting makes sure if one month (or abbr) is a prefix of another it
    // will match the longer piece.
    shortPieces.sort(cmpLenRev);
    longPieces.sort(cmpLenRev);
    mixedPieces.sort(cmpLenRev);
    for (i = 0; i &lt; 12; i++) {
        shortPieces[i] = regexEscape(shortPieces[i]);
        longPieces[i] = regexEscape(longPieces[i]);
        mixedPieces[i] = regexEscape(mixedPieces[i]);
    }

    this._monthsRegex = new RegExp('^(' + mixedPieces.join('|') + ')', 'i');
    this._monthsShortRegex = this._monthsRegex;
    this._monthsStrictRegex = new RegExp('^(' + longPieces.join('|') + ')', 'i');
    this._monthsShortStrictRegex = new RegExp('^(' + shortPieces.join('|') + ')', 'i');
}
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