a strftime helper for js Date objects

dateformat.js

/* Allows js Dates to return an object with formatted information
 *
 * The object has the same signature as php.net/date, so you can
 * use that table to look up what the keys are. 
 * Most numbers are returned as strings so they can be 0 padded.
 * not all keys are represented, but it's enough to save you time.
 * no license, go nuts or whatever, or don't
 * [email protected]
 */
Date.prototype.format = function(){
  var months = ["January","February","March","April","May","June",
    "July","August","September","October","November","December"];
  var days = ["Sunday","Monday","Tuesday","Wednesday","Thursday",
    "Friday","Saturday","Sunday"];
  return formats = {
    // years, 4 and 2 digit verions
    "Y":this.getFullYear()+"",
    "y":(this.getFullYear()+"").slice(2,4),
    
    // months: 3 letter abbrs, full month, 0 padded month number
    "M":months[this.getMonth()].slice(0,3),
    "F":months[this.getMonth()],
    "n":(this.getMonth()+1) < 10 ? "0"+(this.getMonth()+1) : this.getMonth()+1,
    
    // day of week: full length, abbreviated, & numerical
    "l":days[this.getDay()],
    "D":days[this.getDay()].slice(0,3),
    "N":(this.getDay() == 0) ? 7 : this.getDay(),
    // this requires a Date.prototype.getWeek function
    // much like: https://gist.github.com/756300
    "W":this.getWeek(),
    
    // zero-padded date and non-padded
    "d":this.getDate() < 10 ? "0"+this.getDate() : ""+this.getDate(),
    "j":this.getDate()+"",
    
    // 24 and 12 hour representations
    "G":this.getHours()+"",
    "g":(this.getHours() % 12 == 0) ?  "12" : (this.getHours() % 12)+"",

    // zero-padded 24 and 12 hour representations
    "H":this.getHours() < 10 ? "0"+this.getHours() : ""+this.getHours(),
    "h":(this.getHours() % 12) < 10 ? 
        ((this.getHours() === 0) ? "12" : "0"+(this.getHours() % 12))
      : ""+(this.getHours() % 12),
    
    // AM/PM, & zero-padded minutes and seconds. milliseconds not padded
    "A":(this.getHours() > 11) ? "PM" : "AM",
    "a":(this.getHours() > 11) ? "pm" : "am",
    "i":this.getMinutes() < 10 ? "0"+this.getMinutes() : ""+this.getMinutes(),
    "s":this.getSeconds() < 10 ? "0"+this.getSeconds() : ""+this.getSeconds(),
    "m":""+this.getMilliseconds(),
    
    // fragile! timezone representation which depends on Date's tostring
    // containing the timezone as (EST|DST|EDT|MST...)
    "T":(/\((\w{3})\)/).exec(this+"") ? (/\((\w{3})\)/).exec(this+"")[1] : "",
    "Z":this.getTimezoneOffset()
  };
};