Lua 脚本

ioredis supports all of the scripting commands such as EVAL, EVALSHA and SCRIPT. However, it's tedious to use in real world scenarios since developers have to take care of script caching and to detect when to use EVAL and when to use EVALSHA. ioredis exposes a defineCommand method to make scripting much easier to use:

JavaScript

const redis = new Redis();

// This will define a command echo:
redis.defineCommand("echo", {
  numberOfKeys: 2,
  lua: "return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}",
});

// Now `echo` can be used just like any other ordinary command,
// and ioredis will try to use `EVALSHA` internally when possible for better performance.
redis.echo("k1", "k2", "a1", "a2", (err, result) => {
  // result === ['k1', 'k2', 'a1', 'a2']
});

// `echoBuffer` is also defined automatically to return buffers instead of strings:
redis.echoBuffer("k1", "k2", "a1", "a2", (err, result) => {
  // result[0] equals to Buffer.from('k1');
});

// And of course it works with pipeline:
redis.pipeline().set("foo", "bar").echo("k1", "k2", "a1", "a2").exec();

If the number of keys can't be determined when defining a command, you can omit the numberOfKeys property and pass the number of keys as the first argument when you call the command:

JavaScript

redis.defineCommand("echoDynamicKeyNumber", {
  lua: "return {KEYS[1],KEYS[2],ARGV[1],ARGV[2]}",
});

// Now you have to pass the number of keys as the first argument every time
// you invoke the `echoDynamicKeyNumber` command:
redis.echoDynamicKeyNumber(2, "k1", "k2", "a1", "a2", (err, result) => {
  // result === ['k1', 'k2', 'a1', 'a2']
});