javascript强大的日期函数代码分享

var date = function( a, s ) {
    var d = s ? new Date( s ) : new Date(), f = d.getTime();
    return ( + a ).replace( /a|A|d|D|F|g|G|h|H|i|I|j|l|L|m|M|n|s|S|t|T|U|w|y|Y|z|Z/g, function ( a ) {
        switch ( a ) {
                case a : return d.getHours() > 11 ? pm : am;
                case A : return d.getHours() > 11 ? PM : AM;
                case d : return ( 0 + d.getDate() ).slice(-2);
                case D : return [ Sun, Mon, Tue, Wed, Thu, Fri, Sat ][ d.getDay() ];
                case F : return [ January, February, March, April, May, June, July, August, September, October, November, December ][ d.getMonth() ];
                case g : return ( s = ( d.getHours() || 12 ) ) > 12 ? s - 12 : s;
                case G : return d.getHours();
                case h : return ( 0 + ( ( s = d.getHours() || 12 ) > 12 ? s - 12 : s ) ).slice(-2);
                case H : return ( 0 + d.getHours() ).slice(-2);
                case i : return ( 0 + d.getMinutes() ).slice(-2);
                case I : return (function(){ d.setDate(1); d.setMonth(0); s = [ d.getTimezoneOffset() ]; d.setMonth(6); s[1] = d.getTimezoneOffset(); d.setTime( f ); return s[0] == s[1] ? 0 : 1; })();
                case j : return d.getDate();
                case l : return [ Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday ][ d.getDay() ];
                case L : return ( s = d.getFullYear() ) % 4 == 0 && ( s % 100 != 0 || s % 400 == 0 ) ? 1 : 0;
                case m : return ( 0 + ( d.getMonth() + 1 ) ).slice(-2);
                case M : return [ Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec ][ d.getMonth() ];
                case n : return d.getMonth() + 1;
                case s : return ( 0 + d.getSeconds() ).slice(-2);
                case S : return [ th, st, nd, rd ][ ( s = d.getDate() ) < 4 ? s : 0 ];
                case t : return (function(){ d.setDate(32); s = 32 - d.getDate(); d.setTime( f ); return s; })();
                case T : return UTC;
                case U : return ( + f ).slice( 0, -3 );
                case w : return d.getDay();
                case y : return ( + d.getFullYear() ).slice(-2);
                case Y : return d.getFullYear();
                case z : return (function(){ d.setMonth(0); return d.setTime( f - d.setDate(1) ) / 86400000; })();
                default : return -d.getTimezoneOffset() * 60;
            };
    } );
};