lib/command/zset.js
function zrank(key, member, req) {
  var zset = this.getKey(key, req);
  if(zset === undefined) return null;
  return zset.zrank(member);
}
function zrank(key, member, req) {
  var zset = this.getKey(key, req);
  if(zset === undefined) return null;
  return zset.zrank(member);
}
function zrank ( key , member , req ) { var zset = this . getKey ( key , req ) ; if ( zset === undefined ) return null ; return zset . zrank ( member ) ; }
Returns the rank of member in the sorted set stored at key,
with the scores ordered from low to high.
Returns the rank of member in the sorted set stored at key with the scores ordered from low to high .