array_search.js

function array_search (needle, haystack, argStrict) {
  // http://kevin.vanzonneveld.net
  // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +      input by: Brett Zamir (http://brett-zamir.me)
  // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // *     example 1: array_search('zonneveld', {firstname: 'kevin', middle: 'van', surname: 'zonneveld'});
  // *     returns 1: 'surname'
  // *     example 2: ini_set('phpjs.return_phpjs_arrays', 'on');
  // *     example 2: var ordered_arr = array({3:'value'}, {2:'value'}, {'a':'value'}, {'b':'value'});
  // *     example 2: var key = array_search(/val/g, ordered_arr); // or var key = ordered_arr.search(/val/g);
  // *     returns 2: '3'

  var strict = !!argStrict,
    key = '';

  if (haystack && typeof haystack === 'object' && haystack.change_key_case) { // Duck-type check for our own array()-created PHPJS_Array
    return haystack.search(needle, argStrict);
  }
  if (typeof needle === 'object' && needle.exec) { // Duck-type for RegExp
    if (!strict) { // Let's consider case sensitive searches as strict
      var flags = 'i' + (needle.global ? 'g' : '') +
            (needle.multiline ? 'm' : '') +
            (needle.sticky ? 'y' : ''); // sticky is FF only
      needle = new RegExp(needle.source, flags);
    }
    for (key in haystack) {
      if (needle.test(haystack[key])) {
        return key;
      }
    }
    return false;
  }

  for (key in haystack) {
    if ((strict && haystack[key] === needle) || (!strict && haystack[key] == needle)) {
      return key;
    }
  }

  return false;
}