Migrating from node_redis

It's not hard to migrate from node_redis to ioredis since ioredis is compatible with node_redis for most APIs. However there are some exceptions:

• constructor. node_redis use var client = redis.createClient() to create a new RedisClient instance, while ioredis prefer to var redis = new Redis(). For compatibility, ioredis supports var redis = Redis.createClient() as well.

• The options passed to the constructor are different. See API#new_Redis.

• ioredis considers null/undefined as empty strings, while node_redis will convert them to "null"/"undefined". For instance:

  // node_redis
  client.set('foo', null);
  client.get('foo', function(_, res) {
    console.log(typeof res, res); // "string", "null"
  });
  
  // ioredis
  redis.set('foo', null);
  redis.get('foo', function(_, res) {
    console.log(typeof res, res); // "string", ""
  });

• Transaction. The result of transaction in node_redis and ioredis are different, for instance:

  // node_redis
  client.multi().set('foo').get('foo').exec(function (err, res) {
    /* err is: 
        [
          [Error: Error: ERR wrong number of arguments for 'set' command],
          [Error: Error: EXECABORT Transaction discarded because of previous errors.]
        ]
       res is undefined
    */
  });
  
  // ioredis
  redis.multi().set('foo').get('foo').exec(function (err, res) {
    /* err is:
       { [ReplyError: EXECABORT Transaction discarded because of previous errors.]
         name: 'ReplyError',
         message: 'EXECABORT Transaction discarded because of previous errors.',
         command: { name: 'exec', args: [] },
         previousErrors:
         [ { [ReplyError: ERR wrong number of arguments for 'set' command]
           name: 'ReplyError',
           message: 'ERR wrong number of arguments for \'set\' command',
           command: [Object] } ] }
       res is undefined
    */
  });
  
  // node_redis
  client.multi().set('foo', 'bar').lpush('foo', 1).exec(function (err, res) {
    /* err is: null
       res is [ 'OK', 'WRONGTYPE Operation against a key holding the wrong kind of value' ]
    */
  });
  
  // ioredis
  redis.multi().set('foo', 'bar').lpush('foo', 1).exec(function (err, res) {
    /* err is: null
       res is [
         [ null, 'OK' ],
         [ { [ReplyError: WRONGTYPE Operation against a key holding the wrong kind of value] } ]
       ]
    */
  });

• Pub/Sub. When you subscribe multiple channels in node_redis, only the first response is included in the callback. For instance:

  client.subscribe('foo', 'bar', function (err, channel) {
    // channel is 'foo'
    // `bar` isn't subscribed now
  });

  However, in ioredis, callback function will be invoked only when all the channels are subscribed, and the result is the channel count that the client is subscribed:

  redis.subscribe('foo', 'bar', function (err, count) {
    // count is 2
    // both `foo` and `bar` are subscribed now
  });