phpjs/experimental/datetime/timezone_name_from_abbr.js

php.js offers community built php functions in javascript

function timezone_name_from_abbr(abbr, gmtOffset, isdst) {
  // http://kevin.vanzonneveld.net
  // +   original by: Brett Zamir (http://brett-zamir.me)
  // -    depends on: timezone_abbreviations_list
  // *     example 1: timezone_name_from_abbr('CET');
  // *     returns 1: 'Europe/Berlin'
  // *     example 2: timezone_name_from_abbr('', 3600, 0);
  // *     returns 2: 'Europe/London'

  var i = 0, t = '', arr = [];
  if (gmtOffset === undefined || gmtOffset === null || gmtOffset === '') {
    gmtOffset = -1;
  }

  var tal = this.timezone_abbreviations_list();
  if (abbr && tal[abbr.toLowerCase()]) {
    arr = tal[abbr.toLowerCase()];
    if (gmtOffset !== -1) {
      for (i = 0; i < arr.length; i++) {
        if (gmtOffset === arr[i].offset) {
          return arr[i].timezone_id;
        }
      }
    }
    return arr[0].timezone_id;
  } else {
    for (t in tal) {
      for (i = 0; i < tal[t].length; i++) {
        if (tal[t][i].offset === gmtOffset && tal[t][i].dst == isdst) {
          return tal[t][i].timezone_id;
        }
      }
    }
  }
  return false;
}