code: function buildEntitiesLookup(items, radix) {
              var i, chr, entity, lookup = {};
              if (items) {
                  items = items.split(',');
                  radix = radix || 10;
                  // Build entities lookup table
                  for (i = 0; i < items.length; i += 2) {
                      chr = String.fromCharCode(parseInt(items[i], radix));
                      // Only add non base entities
                      if (!baseEntities[chr]) {
                          entity = '&' + items[i + 1] + ';';
                          lookup[chr] = entity;
                          lookup[entity] = chr;
                      }
                  }
                  return lookup;
              }
          }
docs: Build a two way lookup table for the entities