Programmer Group

Enterprises usually attach great importance to network security because of the importance of business, so a good firewall system is a powerful weapon!In this article, we will learn about the basic principle of the new firewall service firewalld of CentOS 7. It has a very powerful filtering system called Netfilter, which is built into the kernel ...

Array object 1. Method of not changing the original array concat() The concat() method is used to join two or more arrays. Parameter: required. This parameter can be a concrete value or an array object. It can be any number. Return value: returns the connected new array var hege = ["Cecilie", "Lone"]; var stale = ["Emil", "Tobias", "Linus ...

1. Effect As we all know, AMG8833 module belongs to a relatively low-end infrared temperature acquisition sensor, with low detection accuracy and poor distance conditions. There is no outline at a distance, but a circle. So this is what I personally think is a good rendering (in fact, that's it). If you don't say much, let's see the effect ...

1. Introduction to PulseSensor (1) Working principle PulseSensor is a photoelectric reflective analog sensor for pulse and heart rate measurement. Wear it on the finger or earlobe, etc. through wire connection, the collected analog signal can be transmitted to stm32, Arduino and other MCU, and analog-to-digital conversion (voltage acquisition ...

DataX is Alibaba's heterogeneous data source offline synchronization tool. For detailed introduction and use, please refer to Introduction to the official website and Quick Start . DataX series mainly introduces the principle of the whole operation in more detail.ConfigurationThe parsing of DataX configuration includes three files: job.json, c ...

Author: Zhang Lianzhuang, PostgreSQL R & D Engineer He has been engaged in the development of PostgreSQL database kernel for many years and has a very in-depth research on citus. In the last issue, we introduced the PostgreSQL data retrieval tool: pg_reconvery This article will take you to understand PG_ The implementation principle and de ...

Vue adopts the component-based development method, so the communication between components is essential: for example, the parent component needs to transfer data to the child component, and the child component informs the parent component of what happens inside it. Therefore, it is particularly important to define a good interface and decouple ...

Principle introduction: Use interrupt to notify, not force Best practice: how to stop threads correctly Normal stopping process (without external interference) The run() method has been executed There was an exception, but it was not caught Correct method: use interrupt to request to stop the thread Normal situation (there is no standard w ...

brief introductionKoa Is a very lightweight web development framework built by the Express team. Compared with Express, Koa uses async function to solve asynchronous problems, and is completely separated from middleware. It is very elegant, and Koa code is concise and friendly, which is very suitable for beginners.Koa code structureYou can see ...

scene The template uses conditional judgment to control the style of the page, which is the most common application. Vue provides two basic methods, one is the ternary operator we have talked about, and the other is v-if. Ternary operators control template styles Let's first look at the use of ternary operators to control the style of te ...