JavaScript 'this' contextual error

I know I know it’s a old question. Actually you can find tons of questions about ‘this’ pointer of JS on StackOverflow or anywhere else. The dogma is really easy that, ‘this’ points to whoever calls it. But, it’s not until you made a mistake and spent half an hour to figure it out that you can say you truely understand what it really says. [read more]

SSH to AWS Elastic Beanstalk

Purpose I need to ssh to AWS Elastic beanstalk EC2 instance to install my Solr client upon it. But EBS automatically created the EC2 and configured everything for me, which skipped all usual setup steps. [read more]

Fixed No-Response Issue on NodeJS

What’s up I’ve been working on web socket application these days for a while. I successfully built web socket between my React app and nodeJS backend and everything works smoothly. became a handy tool that helps a lot with my project so I decided to keep on using it for my other side of connection, which establishes socket between NodeJS and hardware running Linux. [read more]

Gadget: Slides Crawler

Background Final finally comes. I need all slides for courses to review. But manually downloading is such a heavy load, both physically and mentally. I used to crawl files using cURL, but if I want to crawl a certain kind of file (i.e. PDF in this case), the solution is not straight-forward. I found wget works perfectly in supporting given type crawling. [read more]

Compute PageRank with Jsoup and NetworkX

Brief By now I have crawled all pages I need by Crawler4j. To index them to serve my search engine, PageRank is a very famous and popular so it’s a good choice. In Page Rank algorithm, directed graph of web pages is the essence of all the calculations. With the help of Jsoup, I can easily build a graph for Page Rank calculation. Then, my transitional result from Jsoup could be enhanced by NetworkX, and transformed into PageRank scores. [read more]

My QT program crashes with no message / reason

My QT crashed tons of times yesterday. With no report message, it took me a lot of time to find out what happened. Eventually, the cause was silly, but it pushed me to know more about C++. [read more]

I made my IPhone into GBA

I just had a fantastic talk with my colleague. We both agreed that fire emblem series on GBA are masterpieces. Afterwards, it made me want to play the most classic one again so much. However, I lost my GameBoy console long ago and I didn’t want to play on my bulk windows laptop either. What if playing on IPhone? Well, apparently Apple wouldn’t let emulators run on IPhone for some reason (which I don’t quite understand). [read more]


Today, I was told that “in our program, only use smart pointer when pointer is necessary”. I got confused at the very beginning and felt that it was another “code of coding” in company. However, when I dug more into it, I found it’s really a great practice to use it everywhere. Here is what I got. [read more]

Quick start for spatial database by PostGIS and Google Earth

Intro Spatial database is the basics of map technology. Now I got chance to implement it. Let’s check how it differs from conventional DBs, and visualize our results in Google Earth using KML format! [read more]

Build Authentication WebApp and APIs by Auth0

Well, I have built my web application with NodeJS and DynamoDB as backend. Now I need to build a login system to fulfill user access. So, all I need to do is building a couple of APIs to update my DBs with username and password, also query by username and match password while logging in … [read more]

Setup Blog with Github Pages & Jekyll

Happy to move in! Lucky for me, I found Github Pages. It’s just like what I dreamed of! I used to host my page on AWS. It was bulky and tough. I had been reinventing different kind of wheels and I’m done with that… Until I found Github Pages then Jekyll! [read more]