Detailed explanation of application cases of redis in nodejs

This time I will bring you a detailed explanation of the application cases of redis in nodejs. What are the precautions for the application of redis in nodejs. The following is a practical case, let's take a look.

redis is an in-memory database with very good performance. It is deployed as a caching data library between the application and mysql data, which can greatly improve the performance of the application. Here is a brief introduction to the nodejs client The demo program for terminal operation of redis

redis can store a total of 5data types, which are string, list, set, three columns, and ordered set; Here, the additions, deletions, checks and modifications of these five data types will be processed one by one;

1. Installation of redis on mac:

https://redis. io/download, the current stable version I am using is 4.0.9. After decompressing, enter the redis-4.0.9 directory, execute make && sudo make install, and wait a few minutes to install it;

2 , redis startup:

Execute redis-server on the command line to start, the default port is 6379;

3. Install nodejs client:

Create the redis-node directory, After yarn init -y in this directory, execute the command: yarn add redis to install the redis client of nodejs. Reference document: https://github.com/NodeRedis/node_redis

4. In redis- In the node directory, execute node on the terminal, and you can execute the nodejs code responsively on the terminal for testing. Let’s start the demo program

First, create a client and connect to the redis server. After executing the following connection Before client code, please make sure that the redis server is running: the terminal provider can execute redis-server, the default port is 6379;

const redis = require('redis');
const client = redis.createClient(); //默认连接localhost:6379，具体配置参数可以参考文档https://github.com/NodeRedis/node_redis

If everything goes well, we have created a client to connect to the redis server. Subsequent operations are performed on the client object.

1. String type

Although it is a string type, the data that can be stored includes strings, integers and floating point numbers.

var res = client.set('name', 'abczhijia', (err, data) => {
 console.log('err: ', err, ' data: ', data);
}); // err: null data: OK，res的值是true
client.get('name', (err, data) => {
 console.log('err: ', err, ' data: ', data);
}); // err: null data: abczhijia

For the sake of simplicity, we define a callback function for outputting data:

const cb = (err, data) => {
 console.log('err: ', err, ' data: ', data, ' data type: ', typeof data);
}

Let’s do a test for integers:

client.set('age', 20, cb); //err: null data: OK data type: string
client.get('age', cb); //err: null data: 20 data type: string

It can be seen that although the setting is an integer, when it is output, it is still a string, so if you want to perform calculations, you need to do the conversion yourself in the callback function

2. List data type

//从右侧推入
client.rpush('friends', 'mike', 'jhon', cb); //err: null data: 2 data type: number
client.lrange('friends', 0, -1, cb); //err: null data: [ 'mike', 'jhon' ] data type: object
//从左侧推入
client.lpush('friends', 'sam', 'bob', cb); //err: null data: 4 data type: number
client.lrange('friends', 0, -1, cb); // err: null data: [ 'bob', 'sam', 'mike', 'jhon' ] data type: object
//从右侧弹出
client.rpop('friends', cb); //err: null data: jhon data type: string
//从左侧弹出
client.lpop('friends', cb); //err: null data: bob data type: string
//打印看看发生了啥
client.lrange('friends', 0, -1, cb); // err: null data: [ 'sam', 'mike' ] data type: object
//查看索引位置的值
client.lindex('friends', 0, cb); // err: null data: sam data type: string
//对列表进行裁剪
client.rpush('friends', 'tom', 'bryant', cb)// err: null data: 4 data type: number
client.ltrim('friends', 1, 2, cb); //err: null data: OK data type: string
client.lrange('friends', 0, -1, cb); //err: null data: [ 'mike', 'tom' ] data type: object

Note here that the list operation can push one or more data from the right rpush, or push one or more data from the left lpush; in addition, when taking the value, you need to specify the start and end Position, if you want to get the entire position, you can write the end position as -1.

3. Collection data type

//往集合ids中加几个元素
client.sadd('ids', 1, 2, cb); //err: null data: 2 data type: number
//查看集合元素
client.smembers('ids', cb); //err: null data: [ '1', '2' ] data type: object
//从集合中删除元素
client.srem('ids', 2, cb); // err: null data: 1 data type: number
//看看发生了啥
client.smembers('ids', cb); //err: null data: [ '1' ] data type: object
//看看集合有多少个元素
client.scard('ids', cb); //err: null data: 1 data type: number
//再加几个元素进去
client.sadd('ids', 3, 5, 8, 9); //
//判断元素是否在集合内
client.sismember('ids', 8, cb); // err: null data: 1 data type: number
client.sismember('ids', 80, cb); //err: null data: 0 data type: number

4. Hash data type

//往散列上添加多组键值对
client.hmset('phone', 'price', 5888, 'name', 'iphonex', cb); //err: null data: OK data type: string
//查看多个键的值
client.hmget('phone', 'price', 'name', cb); //err: null data: [ '5888', 'iphonex' ] data type: object
//查看键值对的数量
client.hlen('phone', cb); //err: null data: 2 data type: number
//删掉其中一个键值对
client.hdel('phone', 'price', cb); //err: null data: 1 data type: number
//看看price是否还在？
client.hmget('phone', 'price', cb); //err: null data: [ null ] data type: object,原来只留下了null
//再加几个属性
client.hmset('phone', 'vendor', 'apple', 'madein', 'china', cb);
//取出所有的键值对
client.hgetall('phone', cb); //err: null data: { name: 'iphonex', vendor: 'apple', madein: 'china' } data type: object
//取出所有的键
client.hkeys('phone', cb); //err: null data: [ 'name', 'vendor', 'madein' ] data type: object
//取出所有的值
client.hvals('phone', cb); //err: null data: [ 'iphonex', 'apple', 'china' ] data type: object
//判断键是否存在
client.hexists('phone', 'name', cb); //err: null data: 1 data type: number
client.hexists('phone', 'price', cb); //err: null data: 0 data type: number

I believe you have read the case in this article After mastering the method, please pay attention to other related articles on the php Chinese website for more exciting content!

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