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  The evolving history of asynchronous operation in JavaScript

JavaScript is single threaded, it means there would be only one task running at any point of time. But this would slow down the overall program execution if there is long running task, hence asynchronous task execution is desired in complex cases. To achieve asynchronous task execution, there are a few options introduced in JavaScript. setTimeout/setInterval Event Promise Async/Await setTimeout/setInterval is one of the first mechanisms introduced in JavaScript to simulate asynchronous operati...

   JAVASCRIPT,ASYNC,PROMISE,AWAIT     2019-11-09 08:21:56

  Load and execute JavaScript

When we load and execute JavaScript in a webpage, there are many points we need to care about because of its design and feature. There are two features about JavaScript execution in a browser: 1). The JavaScript codes will be executed immediately once loaded;2). When JavaScript codes are being executed, they will block the following contents (including page rendering and other resources downloading). So if there are multiple js files to be loaded, these codes will be executed sequentially. Since...

   JavaScript,async,defer,load,execute     2013-06-07 04:53:46

  Set file permission in Java

Prior to Java 6,  there is no good solution at the Java level to provide file permission management. You need to implement your own native methods or call the Runtime.exec() to invoke the system routine such as chmod in LInux. Since Java 6, Java introduces a set of methods which can be used to set the file permission at Java level. These methods include: File.setReadable(boolean); File.setWritable(boolean); FIle.setExecutable(boolean); File.setReadable(boolean, boolean); File.setWritable(bo...

   JAVA, FILE PERMISSION, POSIX,learnjava     2015-08-29 03:37:37

  Guide on recovering data in MySQL

In our daily work, there might be mistakes made which got some data or even databases deleted in MySQL. If this happens on production, it would be a nightmare. In case this happens, normally DBA would jump in to save the world. And they would try to recover the data from the backup if there is any. But if there is no backup, then the show stops. Hence database backup is necessary on production environments to avoid such awkward situation. Also normally in MySQL, binlog should be enabled as well ...

   MYSQL,DATABASE,BACKUP,BINLOG,EXAMPLE     2020-08-26 07:50:30

  3 meanings of Stack

We may frequently see stack when we read programming books. But many times we may be confused about the different meanings of it. This term actually has three common meanings. Here we explain the three different meanings of Stack in programming. 1. Data structure The first meaning of Stack defines a method for storing data. Its feature is LIFO9Last In First Out). In this data structure, data are accumulated level by level. The data last put in is added at the top of the stack. When using the dat...

   Stack,Memory,Data structure     2014-02-24 04:56:46

  Chrome extension to display desktop notification

Have you ever thought about writing extension for web browsers so that we can complete some tasks easily. Do you think writing extension for browsers is very difficult? You have no clue where to begin? On Chrome, this isn't any problem now as long as you know how to write HTML,CSS and JavaScript. We will show one example of Chrome extension today. The extension will display a desktop notification on your desktop. You need to create two files here, one is the notification.json which is the config...

   Chrome extension,Desktop notification,Example     2013-06-29 22:23:51

  Meta tag in HTML header

In server response, we can use response.setHeader() to set the meta information in header of a HTML page. The usage is response.setHeader(name,context); meta is used to simulate the response header of HTTP protocol in HTML page. It should be put between the <head> and </head> tag. 1. <meta name="Generator" content="" > <!--This is to specify the tool which generates this page such as Microsoft FrontPage 4.0 etc --> 2. <meta name="keywords" content=""> <!-- To tel...

   HTTP,meta,HTML,head     2013-05-22 11:34:08

  A mini post on GoLang context

In a GoLang web server, every request coming in will be handled by a goroutine. In the request handler, the logic may also need to create new goroutine to handle other tasks like RPC call. When the request is processed and response is returned, these goroutines created need to be exited so that no goroutine leak should happen. package main import ( "fmt" "log" "net/http" ) func main() { http.HandleFunc("/echo", func(w http.ResponseWriter, r *http.Request) { fmt.Println(&r) w.Write(...

   CONTEXT,GOLANG     2019-12-14 06:21:02

  SameSite attribute in cookie

Starting from Chrome 51, a new attribute SameSite has been introduced for browser cookie. This attribute is to prevent CSRF attack. Cookie is normally used to store data exchanged between client and server. It frequently stores user login information. If a malicious website can forge a HTTP request with the valid third party website cookie, it may be called a CSRF attack. For example, if a user logins to a bank website your-bank.com, the bank server responds a cookie: Set-Cookie:id=a3fWa; L...

   JAVASCRIPT,COOKIE,SAMESITE,CHROME,CSRF     2019-09-14 04:57:51

  errGroup in GoLang explained

Today, let's talk about the usage and applicable scenarios of errGroup, which is often used. Why is it useful? Generally, when we use goroutine, we cannot return a value. If you want to pass out the result of the goroutine execution, you usually have to use the channel. The errGroup package is suitable if you want to know when the goroutine you opened encounters an error during execution and stop working, and I need to know the error value. errGroup usage The package needs to be downloaded and i...

   GOLANG,ERRGROUP,WAITHROUP,CONCURRENCY     2023-05-27 23:58:20

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