SEARCH KEYWORD -- variable


  Why do I need a debugger?

  When I begin to learn a new programming language, I will try and master the debugger for it as early as possible. For example, in 2013, while I touched the Go, there seems only gdb for use. Although gdb itself is not a good choice (From Debugging Go Code with GDB): As a consequence, although GDB can be useful in some situations, it is not a reliable debugger for Go programs, particularly heavily concurrent ones. But at that time there was no other choice. So after delve&nb...

       2017-07-21 22:53:16

  Regular expression to get html meta description

When we need to process a HTML page source code, we often need to retrieve the meta description of the page besides the links in the page. This description is usually located in <meta> tag of a HTML page. The meta description is very useful for search engine index. How can we retrieve the meta description? If we use a regular expression, we can easily get the meta description. In JavaScript, the regular expression looks like : var pattern = /<meta.*?name="description".*?content="(.*?)"....

   Regular expression,meta description,HTML,JavaScript     2012-07-03 10:09:20

  How to Set Spring profile With Example

Technology:  Spring Profiles provides a way to isolates the parts of application configuration, it will make available only in certain environments. It is mainly useful it wants to load spring beans based on environment configuration, for example if the operating system is windows we can load some specific spring beans, if it is other than load different spring beans. One more scenario where spring profiles widely used, like for QA environment we will use some database which is hosted local...

   JAVA,PROFILE,SPRING,DEVELOPMENT,APPLICATIONS     2018-07-20 01:17:23

  Three ways to define class in JavaScript

In object oriented programming, class is the template of object, it defines the properties and methods of a group of objects. Unfortunately, JavaScript doesn't support class, but we can have some workarounds to simulate class.1. Constructor functionThis is the classical approach, it is also the approach mentioned in many text books. It uses the constructor function to simulate class and it uses the keyword this to represent the object internally.function Cat() {　　this.name = "Kelly...

   JavaScript,Class,Method,Private,Inheritance     2012-07-09 11:59:51

  Interesting Hello World

Hello world is the beginning of everything. When you first learn a new programming language, the first program you write is to print the "Hello world" string on the console with that language. For example: So who invented "Hello world"? It's Brian Kernighan, a canadian computer scientist and author of The C Programming Language and The Unix Programming Environment. In his books, he used to write "Hello world" which changed the whole world. Also programmers like to use foo and bar as variable n...

   Programming,History     2013-08-29 11:31:00

  One thought about JavaScript exception handle

Due to network, browser and cache issues, the JS executed in production may produce different results from the testing environments. Sometimes they may produce exceptions. Front-end developers may encounter this kind of exceptions frequently. But how to log and use them is seldomly considered by them. Actually, exception handling includes two steps : log and use. 1. Log Regarding to log error, this is relatively convenient, since in each browser, there is one interface called window.onerror. win...

   JaavScript,Log,Exception,Email     2013-03-18 12:50:21

  Set Real-Time Clock Unit for OT/IoT Device

Configure DS1307 RTC on BeagleBone-Black Arduino or Raspberry-PI Figure-00: Project Overview Diagram , version v0.1.2 (2024) Program Design Purpose: Real-Time Clock (RTC) modules are essential for maintaining accurate timekeeping in various applications, including system clocks, data logging, and alarm systems. In scenarios where devices operate offline, such as a ship's NMEA 0183 data recorder that logs engine and rudder data, or an RTU (Remote Terminal Unit) with real time state change config...

       2024-08-18 03:09:06

  this in JavaScript

this is a keyword in JavaScript. It refers to an internal object created automatically when a function executes, it can only be used in a function. For example:        function test(){ 　　　　this.x = 1; 　　}The this keyword will change when a function is called in different situations. However, the general rule is : this refers to the object which calls the function.Next we discuss the use of this in 4 different situatio...

   this,keyword,use,JavaScript     2012-05-05 12:47:37

  What does session_destroy() do in PHP?

In PHP manual, the description for session_destroy() function is : session_destroy() destroys all of the data associated with the current session. It does not unset any of the global variables associated with the session, or unset the session cookie. To use the session variables again, session_start() has to be called. I am confused about this description. If this function destroys all session data, then why the global variables associated with the session are not unset? Why can we u...

   session_destroy,session_start     2013-08-31 09:59:05

  Three images to understand immutability of String in Java

String is immutable in Java. This means once a String object is created and instantiated, that object cannot be changed. Any operation on the String object will create a new Object instead of operating on the original content. Below are three images to help you understand String immutability in Java. Declare a String String s = "abcd"; s stores the reference to the string content created in the heap. Assign the String reference to another String variable String s2 = s; s2 stores the same ...

   STRING,JAVA     2016-03-11 20:58:28

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