Properly execute Lua script with node_redis client

I'm trying to write an extremely simple Lua script to access the hyperloglog functionality in redis from node_redis. I have 1 key and multiple hashes as elements to pass. I can successfully do this only if I hard code the key and argument as in the following:

script: 'return redis.call("pfadd", 'testkey', 'valvalval')'

While this works perfectly, this is not very useful...

I've tried every possible way I can think of to access KEYS and ARGV arrays and this is what I currently have in my .js file:

var script = '\
local val = 0 \
for _, hash in pairs(ARGV) do \
     redis.call("pfadd", KEYS[1], hash) \
end \
return val';

And to call my script:

redisInstance.eval(script, 1, args, function (ret) {
    console.log(ret);
});

args is an array as follows:

['key','hash1','hash2','hash3', ...,'hash30']

The callback is always null and no keys are set on the server... The KEYS and ARGV arrays are not accessed... (when hardcoded as I said, it works fine..)

I need to pass all of the hashes as elements (total of about 30 each time) and receive the integer replies.

Thanks in advance for the help.