A simple way to read and write Redis databases in node.js applications _node.js

Before you begin this article, be sure to install the Redis extensions for Redis and Node.js and Node.js--node_redis

First create a new folder and new text file app.js the contents of the file are as follows:

var Redis = require ("Redis")
  , client = Redis.createclient ();
 
Client.on ("Error", function (err) {
  Console.log ("error" + err);
});
 
Client.on ("Connect", runsample);
 
function Runsample () {
  //Set a value
  client.set ("String Key", "Hello World", function (err, reply) {
    console. Log (reply.tostring ());
  });
  Get a value
  client.get ("string Key", function (err, reply) {
    console.log (reply.tostring ());}
  );

When connected to the Redis, the Runsample function is called and a value is set, followed by a readout of the value, running as follows:

OK
Hello World

We can also use the EXPIRE command to set the expiration time of an object, as follows:

var Redis = require (' Redis ')
  , client = Redis.createclient ();
 
Client.on (' Error ', function (err) {
  console.log (' error ' + err);
});
 
Client.on (' Connect ', runsample);
 
function Runsample () {
  //Set a value with the Expiration
  client.set (' string key ', ' Hello World ', redis.print); 
   
    //Expire in 3 seconds
  client.expire (' string key ', 3);
 
  This is the ' only ' to Demo ' TTL
  //runs every second until the timeout
  //occurs on the value
  var myt Imer = setinterval (function () {
    client.get (' string key ', function (err, reply) {
      if (reply) {
        Console.log (' I Live: ' + reply.tostring ());
      } else {
        cleartimeout (mytimer);
        Console.log (' I expired ');
        Client.quit ();
      }
    });
  }, 1000);


   

Note: The timer used above is only to demonstrate the EXPIRE command, you must use the timer carefully in the Node.js project.

The output from running the above program is:

Reply:ok i Live:hello World i live:hello World I live:hello World I
expired

Next we check how long a value is persisted before it expires:

var Redis = require (' Redis ')
  , client = Redis.createclient ();
 
Client.on (' Error ', function (err) {
  console.log (' error ' + err);
});
 
Client.on (' Connect ', runsample);
 
function Runsample () {
  //Set a value
  client.set (' string key ', ' Hello World ', redis.print);
  Expire in 3 seconds
  client.expire (' string key ', 3);
 
  This is the ' only ' to Demo ' TTL
  //runs every second until the timeout
  //occurs on the value
  var myt Imer = setinterval (function () {
    client.get (' string key ', function (err, reply) {
      if (reply) {
        Console.log (' I Live: ' + reply.tostring ());
        Client.ttl (' string key ', Writettl);
      } else {
        cleartimeout (mytimer);
        Console.log (' I expired ');
        Client.quit ();
      }
    });
  }, 1000);
 
function Writettl (err, data) {
  Console.log (' I live for this long yet: ' + data);
}

Run Result:

 Reply:ok i Live:hello world I live for this long yet:2 i Live:hello world I live for t His long yet:1 i Live:hello world I live for this long yet:0 I expired