How to save javascript array as redis list

Question

The following code save the whole array as single value in redis list. But I want to save array values individually. How can I do it?

P.S So sorry for poor English.

var redis = require('redis'),
    client = redis.createClient();

var arr = [1,2,3];

client.rpush('testlist',arr);

Ranjiv

You want to iterate through the array elements and insert them individually. You can write a simple for loop or use Array.prototype.forEach. – Roentgenoscope

Answer 1

Use multi() to pipeline multiple commands at once:

var redis = require('redis'),
    client = redis.createClient();

var arr = [1,2,3];

var multi = client.multi()

for (var i=0; i<arr.length; i++) {
    multi.rpush('testlist', arr[i]);
}

multi.exec(function(errors, results) {

})

And finally call exec() to send the commands to redis.

Maurey

Using redis-node that wasn't working for me, slightly modified here: gist.github.com/vainrobot/141b2162e1200f7c7855 – Alterative

Answer 2

Even if @gimenete answer works, the best way to do what you want is to forward the list elements as arguments to rpush like so:

var redis = require('redis'),
    client = redis.createClient();

var arr = [1,2,3];
client.rpush.apply(client, ['testlist'].concat(arr));

// ... or with a callback
client.rpush.apply(client, ['testlist'].concat(arr).concat(function(err, ok){
  console.log(err, ok);
}));

Pros: - a single instruction will be transmited to Redis

Cons: - a corner-case: .apply will throw a RangeError: Maximum call stack size exceeded if the arguments list length passed to rpush is too large (a little over 100 000 items for v8).

From MDC:

The consequences of applying a function with too many arguments (think more than tens of thousands of arguments) vary across engines (JavaScriptCore has hard-coded argument limit of 65536), because the limit (indeed even the nature of any excessively-large-stack behavior) is unspecified. Some engines will throw an exception. More perniciously, others will arbitrarily limit the number of arguments actually passed to the applied function.

Sigrid

Not work for me. Error: ERR wrong number of arguments for 'rpush' command. – Ranjiv

Exactly as you type . There is no other code in my node js file. – Ranjiv

Sorry, that is the problem with my redis server. I use it on window and can't execute RPUSH with multiple value. – Ranjiv

Answer 3

import { createClient } from "redis";

const redisClient = createClient();

const arr = [1, 2, 3];

async function cacheList() {
  await Promise.all(arr.map((elem) => redisClient.rPush("testlist", elem)));
}

Bechtold

Thank you for your interest in contributing to the Stack Overflow community. This question already has a couple of answers—including one that has been extensively validated by the community. It would be useful to explain how your approach is different, under what circumstances your approach might be preferred, and/or why you think the previous answers aren’t sufficient. Can you kindly edit your answer to offer an explanation? – Christean