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  Understand Virtual DOM

With the popularity of React, the internals and implementation of Virtual DOM has becoming top discussed topic in tech communities and interviews. This post will give an introduction of Virtual DOM and how to implement a simple Virtual DOM logic. How to understand Virtual DOM In early days, front end developers would update a webpage view based on the data status change(usually after making AJAX call). But it brings performance penalties when there is frequent update as it would cause page reflo...

   JAVASCRIPT,DOM,VIRTUAL DOM     2019-12-07 23:43:04

  String.length() vs String.getBytes().length in Java

In Java, String.length() is to return the number of characters in the string, while String.getBytes().length is to return the number of bytes to represent the string with the specified encoding. By default, the encoding will be the value of system property file.encoding, the encoding name can be set manually as well by calling System.setProperty("file.encoding", "XXX"). For example, UTF-8, Cp1252. In many cases, String.length() will return the same value as String.getBytes().length, but in some ...

   Java,UTF8,String,Encoding,Sample     2015-04-01 22:22:23

  How expensive is a MySQL query?

Database access speed is always the bottle neck of many applications. Many application have large amount of data to search, retrieve and display nowadays. How do we improve the performance of our applications, how do we reduce the cost of database access? Apart from the design of database, the quality of the query is also one important factor to take care.  But before that, we need to know how much network traffic a query will consume. Yunyang,Zhang from Nubee in Singapore did some research...

   MySQL,Network traffic,Query     2013-04-09 05:13:33

  Hash Tables in Javascript

IntroductionHash tables are a permutation of associative arrays (i.e. name => value pairs). If you use PHP, then you are very familiar with this type of data structure already since all PHP arrays are associative.The Javascript language implements very loose and somewhat limited support for associative arrays. Any JavaScript array can use other objects as keys, making it a hash, but there exists no formal constructor for initializing them and it is more or less unweildy to work with. A short ...

   JavaScript,Hashtable,Implementation,Array     2011-11-26 02:43:40

  Simple Animation in the HTML5 Canvas Element

HTML5 is generating all kinds of buzz these days. Some of the buzz is about HTML5 being a replacement for Adobe’s Flash. I don’t think it’s there yet but it’s certainly on the way to changing the way content is presented on the web. This is a description of a very simple animation in an HTML5 canvas element. It is coded for readability and not for optimized operation. We’ll add a canvas element to a web page and then use javascript to draw on it. We will...

   HTML5,Canvas,Animation,Sample code     2011-07-01 10:20:08

  Understand GoLang WaitGroup internals and how it works

Background Before getting into the main content, let me give a brief introduction to WaitGroup and its related background knowledge. Here, the focus is on the basic usage of WaitGroup and the fundamental knowledge of system semaphores. For those who are familiar with these, you can skip this section directly. WaitGroup WaitGroup is one of the most common concurrency control techniques in Golang, and its function can be roughly compared to the join() in concurrency control of other languages' mul...

   GOLANG,WAITGROUP,SOURCE CODE     2023-04-26 08:02:01

  JavaScript interview questions

This post will cover the JavaScript questions I have encountered and have seen during my programming career. They will mainly focus on vanilla JavaScript though there are lots of excellent frameworks out there and many people are using them in their daily work. this keyword this keyword is an very important but easy to confuse concept in JavaScript since it is always referring to the calling object of the function. 1. What will be the output of below code snippet? function User(name) { this....

   JAVASCRIPT,ALGORITHM,THIS,CLOSURE     2019-03-09 07:05:46

  Debunking the Google Interview Myth

Years ago, rumors used to circulate about Microsoft interviews.  They were the hot, new company that everyone wanted to work.  With envy came the urban myths.  These rumors have since been transfered to Google, and will surely be transfered to some new company in due time. Bloggers – always desperate for links and traffic – have capitalized on this, with scary articles about their “nightmare interview” and “crazy questions“.  Let’...

   Google,Microsoft,Business insider,Interv     2011-04-26 10:09:53

  Transparency in Cloud Services

37signals recently launched public “Uptime Reports” for their applications (announcement). The reaction on Hacker News was rather tepid, but I think it’s a positive development, and I applaud 37signals for stepping forward. Reliability of cloud applications is a real concern, and there’s not nearly enough hard data out there. Not all products are equally reliable; even within 37signals, the new reports show a 3:1 variation in downtime across apps. That said, ...

   Cloud,Transapency,37signals,Announcement     2012-01-10 07:24:02

  Before Python

This morning I had a chat with the students at Google's CAPE program. Since I wrote up what I wanted to say I figured I might as well blog it here. Warning: this is pretty unedited (or else it would never be published :-). I'm posting it in my "personal" blog instead of the "Python history" blog because it mostly touches on my career before Python. Here goes.Have you ever written a computer program? Using which language?HTMLJavascriptJavaPythonC++COther - which?[It turned out the students ha...

   Python,History,Programming language,B     2012-01-18 08:08:53

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