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  Understand this in JavaScript

In JavaScript, this is always pointing to the owner of a function or a method. Function Let's check out function first. function introduce() {      alert("Hello, I am Laruence\r\n"); } For this function, what does this point to? In JavaScript, a global function's owner is the current page, i.e, the window object. Because its a method of the window object if we define a global function. Now you should know the this will point to the window object in the above function. ...

   JavaScript,this,event,call     2013-04-03 04:10:03

  Understanding JavaScript closure and where it can be used

Closure The official definition of closure is: an expression (usually a function) that has many variables and is bound to an environment that includes those variables. In JavaScript, closure refers to the ability of a function to access the lexical scope in which it was defined, even after the function has been executed and left that scope. This ability is due to the fact that when a function is created, it generates a closure that includes a reference to the definition environment of the curr...

   CLOSURE,JAVASCRIPT,USAGE     2023-03-05 02:17:08

  Valid JavaScript variable names

Did you know var π = Math.PI; is syntactically valid JavaScript? I thought this was pretty cool, so I decided to look into which Unicode glyphs are allowed in JavaScript variable names, or identifiers as the ECMAScript specification calls them. Reserved words The ECMAScript 5.1 spec says: An Identifier is an IdentifierName that is not a ReservedWord. The spec describes four groups of reserved words: keywords, future reserved words, null literals and boolean lite...

   JavaScript,Name convention,Standard     2012-02-22 05:16:53

  Are You a Good Programmer?

If someone asks you to recommend a good programmer, who comes to mind? Do you consider yourself a good programmer? What criteria do you use to judge? In thinking about this, I realized that there are different ways that a programmer can be good. So I present to you The Four Kinds of Good Programmers. And in celebration of Whyday, I include quirky Why-styled illustrations* for your viewing pleasure! The Philosopher The PhilosopherThe philosopher loves to write well-defined, well-structured...

   Programmer,Inventor,Philosopher,Conquero     2011-08-23 07:56:26

  JavaScript: Private variables

The first thing you often hear when talking about JavaScript is often “JavaScript doesn’t have visibility modifiers, hence it doesn’t support private variables”. This is only valid for 50%, because JavaScript indeed doesn’t have visibility modifiers (public, private, friend) but it has closures and function scopes. With these tools we can make variables private. Let’s take the following function: var names = ["Kenneth", "John", "Marc", "Robert"]; var lookup =...

   JavaScript,private variable,closure     2012-04-28 11:46:34

  static nested and non-static nested class in Java

Nested classes are divided into two categories: static and non-static(inner). Nested classes that are declared static are simply called static nested classes. Non-static nested classes are called inner classes. Static class can be defined as : class OuterClass{ static class StaticNestedClass{ //OTHER STUFF } } Static nested classes are accessed using the enclosing class name: OuterClass.StaticNestedClass For example, to create an object for the static nested class, use this synta...

   Java,static nested class,inner class     2014-04-23 07:11:44

  A Perl Regular Expression That Matches Prime Numbers

perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' Can you figure out how it works? I give an explanation below, but try to figure it out yourself. Here is what happens when you run it: $ perl -lne '(1x$_) =~ /^1?$|^(11+?)\1+$/ || print "$_ is prime"' 1 2 2 is prime 3 3 is prime 4 5 5 is prime 6 7 7 is prime 8 9 10 11 11 is prime Here is how it works. First, the number is converted in its unary representation by (1x$_). For example, the number 5 gets converted into 1x5, which is ...

   Perl,Regex,Regular expression,Prime number,One line     2011-12-26 08:42:00

  Test-Driven Development? Give me a break...

Update: At the bottom of this post, I've linked to two large and quite different discussions of this post, both of which are worth reading... Update 2: If the contents of this post make you angry, okay. It was written somewhat brashly. But, if the title alone makes you angry, and you decide this is an article about "Why Testing Code Sucks" without having read it, you've missed the point. Or I explained it badly :-)Some things programmers say can be massive red flags. When I h...

   Test driven,Application design,tool     2011-10-17 10:19:16

  Networking Terminologies

Portmaps sudo apt-get install -y portmap Portmap is a part of ONC RPC (Open Network Computing Remote Procedure) collection of software for implementing remote procedure calls between Computer Programs. It is widely used by NFS (Network File System) and NIS. Portmap is a server that converts RPC program number to DARPA protocol port number. It must be used in order to make RPC calls. Network Infomation Service (NIS) sudo apt-get install -y nis NIS is a client server directory service provi...

   Linux,Network programming,Network file system     2012-02-16 06:22:30

  jQuery to check whether checkbox is checked

In Vanilla JavaScript, the correct way of checking whether a checkbox is checked is to get the property checked of the checkbox. Assuming there is an checkbox with id "checkbox1", below line will return true if the checkbox is checked while it will return false if the checkbox is unchecked: document.getElementById("checkbox1").checked In jQuery, there are a few ways to check this. The first one is to using the corresponding counterpart of the Vanilla JavaScript, it is to check the checked proper...

   jQuery,checked,checkbox,attr,prop     2015-07-25 08:49:54

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