• What problem does promise solve?


    My GitHub blog https://github.com/zhangxingua/blog We all know that promise solves the problem of callback to hell. When it comes to callback hell, it’s easy to think of the followingMisleading pictures: But what is hell? What’s wrong with it? Is it because nesting doesn’t look good or it’s inconvenient to read? First of all, let’s think […]

  • 51. N queen


    The n-queen problem studies how to place n queens on N × n chessboard and make them unable to attack each other. The figure above shows a solution to the 8 queen problem. Given an integer n, the solution of all the different N queens problem is returned. Each solution contains a clear chess placement […]

  • Using token authentication with websocket and spring security


    Introduction to using framework spring boot 1.4.3.RELEASE spring websocket 4.3.5.RELEASE spring security 4.1.3.RELEASE sockjs-client 1.0.2 stompjs 2.3.3 Project introduction Because the company needs to use websocket to actively push messages to the front-end users, the company’s project is a micro service project automatically generated by jhipster, and spring boot itself integrates websocket, so we don’t […]

  • 52. N Queen II


    The n-queen problem studies how to place n queens on N × n chessboard and make them unable to attack each other. The figure above shows a solution to the 8 queen problem. Given an integer n, returns the number of different solutions for Queen n. Example: Input: 4Output: 2Explanation: 4 there are two different […]

  • Configure | electronic + Vue + TS + SQLite configuration


    From the point of view of programming model, using declarative language to declare style and layout, and using functional programming language to write business logic is the best practice of GUI program. Recently I want to write a personal project, so I naturally want to use the front end to write the interface. With the […]

  • Problems in learning jQuery for the first time


    jQuery JQuery first impression I always hear that jQuery is very easy to use, especially when setting styles, it encapsulates many methods to make others use it better. I tried it for the first time today and found many problems Problems in using jquery When used, it often appearsReferenceError:$ is not defined, may be used […]

  • The listener supports no services Oracle


    Questions appear: [[email protected] ~]$ lsnrctl status …… The listener supports no servicesThe command completed successfully   SQL> conn sys/[email protected]:1521/orcl as sysdbaERROR:ORA-12514: TNS:listener does not currently know of service requested in connectdescriptor   Solution: SQL> alter system set local_listener='(ADDRESS=(PROTOCOL=TCP)(HOST=’; System altered.   Verification: [[email protected] ~]$ lsnrctl status …… Service “orcl” has 1 instance(s). Instance “orcl”, status […]

  • Preparing Hadoop and mongodb environments in tumblefeed


    Background: data access on Hadoop and mongodb is required for learning distributed crawlers.Operating system: tumbling update to 20180420+ The DFS of Hadoop stored in HTML and mongodb used to store crawling tasks need to be prepared for the crawler. Although the courseware already contains the redis part, the actual progress code of the course does […]

  • Learning jsonp


    jsonp I’ve learned it before, but I was quite ignorant at that time. I forgot all about it. This time, I should review jsonp once, A kind of This is to solve the cross domain problem of the client. The server can solve the cross domain problem simply by adding a request header const express […]

  • About the SVN submission file, the solution of vscode saving file with read-only status prompt


    About the SVN submission file, vscode saves the file with a read-only status prompt. ​ After Google Baidu has no solution and no peer, friend or official support, I pondered and finally built a set of mature and perfect solutions. Now let’s share this happy moment with you.The specific scheme is as follows:1. Right click […]

  • Self inspection list of Vue knowledge points (2)


    Three questions Are you an engineer who writes code and implements it?Are you an engineer who will evolve in addition to meeting the daily business decline?Are you a qualified Vue developer?If you don’t have an exact answer, you can use the following questions to check yourself See self inspection list of Vue knowledge points for […]

  • MySQL MHA /usr/share/perl5/vendor_perl/MHA/ServerManager.pm, ln301] install_driver(mysql) failed: Attempt to reload DBD/mysql.pm aborted


    In the company, I found three testing machines to build an MHA. The following problem has been tossed for three days. I haven’t met it before. I checked the OS version and found that it was the same. Maybe it was the OS made by different people. I know that the problem of cpan is […]