Date.formatCodeToRegex = function()

in benchmarks/JetStream2/SunSpider/date-format-xparb.js [172:277]
106 lines of code
28 McCabe index (conditional complexity)

Date.formatCodeToRegex = function(character, currentGroup) {
    switch (character) {
    case "D":
        return {g:0,
        c:null,
        s:"(?:Sun|Mon|Tue|Wed|Thu|Fri|Sat)"};
    case "j":
    case "d":
        return {g:1,
            c:"d = parseInt(results[" + currentGroup + "], 10);\n",
            s:"(\\d{1,2})"};
    case "l":
        return {g:0,
            c:null,
            s:"(?:" + Date.dayNames.join("|") + ")"};
    case "S":
        return {g:0,
            c:null,
            s:"(?:st|nd|rd|th)"};
    case "w":
        return {g:0,
            c:null,
            s:"\\d"};
    case "z":
        return {g:0,
            c:null,
            s:"(?:\\d{1,3})"};
    case "W":
        return {g:0,
            c:null,
            s:"(?:\\d{2})"};
    case "F":
        return {g:1,
            c:"m = parseInt(Date.monthNumbers[results[" + currentGroup + "].substring(0, 3)], 10);\n",
            s:"(" + Date.monthNames.join("|") + ")"};
    case "M":
        return {g:1,
            c:"m = parseInt(Date.monthNumbers[results[" + currentGroup + "]], 10);\n",
            s:"(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)"};
    case "n":
    case "m":
        return {g:1,
            c:"m = parseInt(results[" + currentGroup + "], 10) - 1;\n",
            s:"(\\d{1,2})"};
    case "t":
        return {g:0,
            c:null,
            s:"\\d{1,2}"};
    case "L":
        return {g:0,
            c:null,
            s:"(?:1|0)"};
    case "Y":
        return {g:1,
            c:"y = parseInt(results[" + currentGroup + "], 10);\n",
            s:"(\\d{4})"};
    case "y":
        return {g:1,
            c:"var ty = parseInt(results[" + currentGroup + "], 10);\n"
                + "y = ty > Date.y2kYear ? 1900 + ty : 2000 + ty;\n",
            s:"(\\d{1,2})"};
    case "a":
        return {g:1,
            c:"if (results[" + currentGroup + "] == 'am') {\n"
                + "if (h == 12) { h = 0; }\n"
                + "} else { if (h < 12) { h += 12; }}",
            s:"(am|pm)"};
    case "A":
        return {g:1,
            c:"if (results[" + currentGroup + "] == 'AM') {\n"
                + "if (h == 12) { h = 0; }\n"
                + "} else { if (h < 12) { h += 12; }}",
            s:"(AM|PM)"};
    case "g":
    case "G":
    case "h":
    case "H":
        return {g:1,
            c:"h = parseInt(results[" + currentGroup + "], 10);\n",
            s:"(\\d{1,2})"};
    case "i":
        return {g:1,
            c:"i = parseInt(results[" + currentGroup + "], 10);\n",
            s:"(\\d{2})"};
    case "s":
        return {g:1,
            c:"s = parseInt(results[" + currentGroup + "], 10);\n",
            s:"(\\d{2})"};
    case "O":
        return {g:0,
            c:null,
            s:"[+-]\\d{4}"};
    case "T":
        return {g:0,
            c:null,
            s:"[A-Z]{3}"};
    case "Z":
        return {g:0,
            c:null,
            s:"[+-]\\d{1,5}"};
    default:
        return {g:0,
            c:null,
            s:String.escape(character)};
    }
}