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  Generate first N prime numbers

Recently I am taking an online course named "Startup Engineering" on coursera. There is one assignment which is to use NodeJS to write a program to generate the first 100 prime numbers. This may be very easy for many people. Here I just want to share with you the code to generate not only the first 100 prime numbers. but also any number of prime numbers. Below is the code snippet: //Helper class to generate prime numbers var PrimeProcessor=(function(){ var primeArray=[]; functio...

   Algorithm,Prime number,NodeJS,coursera,JavaScript     2013-06-29 22:08:22

  + operation on JavaScript objects

In JavaScript, there are two types of values: primitive and object. Primitives consist undefined, null, boolean, number and string. Other values such as array and function are objects. When applying + operation on different type of values, there would be three kinds of type conversion. Primitive conversion Number conversion String conversion There three type conversions have corresponding abstract operations in JavaScript: ToPrimitive(), ToNumber(), ToString(). For number additi...

   JAVASCRIPT,PROGRAMMING     2018-10-12 22:19:12

  What have been Facebook’s greatest technical accomplishments?

To maintain a large website which gets billions of requests er day and keeps very fast response speed is not an easy task. Many big companies are trying best to improve user experience by adopting different techniques. There is a question on Quora which asks "What have been Facebook’s greatest technical accomplishments?". There is a person who worked in Facebook before provided an answer which helps us understanding how Facebook handles huge amount of traffic each day. Here is the answer f...

   Facebook, Design, Efficiency     2013-01-15 07:32:07

  Reducing Code Nesting

"This guy’s code sucks!" It’s something we’ve all said or thought when we run into code we don’t like. Sometimes it’s because it’s buggy, sometimes it’s because it conforms to a style we don’t like, and sometimes it’s because it just feels wrong. Recently I found myself thinking this, and automatically jumping to the conclusion that the developer who wrote it was a novice. The code had a distinct property that I dislike: lots of ...

   Code nesting,Readability,Maintainability,Reduction     2012-01-02 08:13:46

  Some tricks and tips for using for range in GoLang

GoLang provides two major ways to loop through elements of array, slice and map. They are for and for range. Many people find that for range is very convenient when don't care about the index of the element. In this post, some tricks and tips would be talked about regarding for range. 1. Loop and get pointer of each element Assume there is a code snippet like below which is to get the pointer of each element in an array and create a new array with the corresponding pointer. arr := [2]int{1, 2} r...

   POINTER,FOR LOOP,GOLANG,FOR RANGE     2020-03-08 01:07:00

  Hexadecimal and long in Java

Today I encountered a hexadecimal operation problem when I was implementing a bit reverse function for integer type. Basically in the implementation, there is an operation which is to do the bit operation & between one long integer and a hexadecimal number 0x00000000FFFFFFFFF. I was expecting that the high 32 bits of the long integer will be zeroed. But unfortunately I didn't get the expected result. The basic implementation is: long num=0x00F0_0000; num = (num>>16) | (num<<16); ...

   Hexadecimal,long,Java,bitwise operation     2014-06-18 23:44:32

  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

  FTP Must Die

The File Transfer Protocol (FTP) is specified in RFC 959, published in October 1985. The attempt in this specification is to satisfy the diverse needs of users of maxi-hosts, mini-hosts, personal workstations, and TACs, with a simple, and easily implemented protocol design.That's from the introduction. Does anyone here know what a TAC is? I don't. I had to look it up, since the acronym wasn't even expanded in the RFC. It took three tries in Google, and I finally found it in some obscur...

   FTP,Future,Death,Trend,Protocol     2012-02-06 08:13:36

  Something you may not know about Shell

Shell is also called command line interface, it is the interface between *nix users and computer. Shell is a program which provides service to access OS kernel services. This article is to introduce some not so well known but useful and interesting knowledge about shell. Wiki shell was born almost at the same time as Unix. The first UNIX shell was written by Ken Thompson in 1971 and its name is Thompson sh. It's older than Linux kernel. The default Shell in most *nix and MacOS is bash, bash was...

   Linux, Unix,Shell,Command     2012-11-24 07:19:47

  Dos and Don’ts in Test automation in your project

Test automation is a vital step for any digital solution. With time, its architecture gets more complex, new features are added, and it acquires more users. Thus, your QA team needs to spend more time and effort to ensure the application usability and smooth user experience with no bugs and defects. So here are the things you need to consider before the start of the automation initiative: Define Success Metrics It’s hard to measure success until you haven’t set up clear goals from t...

   TESTING,TEST AUTOMATION     2021-01-12 05:57:45

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