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  PHP to get access token for Facebook app

Since Facebook is now using OAuth 2.0 to authenticate apps to access user information. the SDK of Facebook has provided developers some useful functions to get authentication done. For example, in PHP SDK, there are getAccessToken(), getLoginUrl() etc. But unfortunately, for me I cannot use getAccessToken() method to get the user access token, it only returns me the app access token. Finally I gave up this approach to get access token for the time being. I may later retry this approach if I have...

   Faceook,PHP,Access token,signed request     2012-03-27 12:37:46

  A strange behavior of printing struct with nested struct in GoLang

Normally when trying to print a struct , we would use %v to show all data of the struct. It will print the default format for each field in the struct. %v the value in a default format when printing structs, the plus flag (%+v) adds field names But recently we observed a strange behavior when printing a struct with nested struct which has a String() string implemented, the %v format prints an 'unexpected' output per our understanding.   Let's see the example snippet first. pa...

   PROGRAMMING,GOLANG     2018-10-29 09:59:49

  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

  The hidden risk of passing slice as function parameter

In Go's source code or other open source libraries, there are lots of cases where a slice pointer is passed to function instead of slice itself. This brings up a doubt why not passing slice directly as its internal is backed by an array pointer to point to underlying data? For example, in log package, the formatHeader function takes a parameter buf as type *[]byte instead of []byte. func (l *Logger) formatHeader(buf *[]byte, t time.Time, file string, line int) {} Let's understand the r...

   GOLANG,SLICE,SLICE POINTER     2020-12-13 06:11:14

  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

  JSON unmarshal in GoLang

In almost all mainstream programming languages, there is either built-in or third-party library to support parse JSON data because it is so popular for organizing and transferring data among different services. In GoLang, the built in json package also provides functions for marshalling and unmarshalling JSON data. Marshalling GoLang struct to a JSON string is relatively simple, just need to call json.Marshal(), it's a bit complicated to unmarshal an arbitrary JSON string into a GoLang struct ob...

   GOLANG,JSON,UNMARSHAL,EMPTY INTERFACE     2019-11-09 21:57:30

  How to monitor user behavior in webpage

Sometimes there is a need for website owners to monitor user behavior on the site so that they can know what pages are mostly visited and which parts are more popular so that they can provide better service to their users. These behavior usually contain user clicks, user mouse over events etc. These data can be sent back to server when triggered with some meta data. In this post, we will cover a few ways to monitor user behavior on a web portal and send data back to backend sever. 1. Synchronous...

   HTML,BEACON API,PING,USER BEHAVIOR     2019-06-29 06:06:59

  Google search now highlights search text in target link page

It seems Google is slowly releasing a new feature to highlight search text when user opens a matching search result link through its search engine.  Now for example if you type something in the Google search bar, you will see normal search results. But when you click the link, e.g, the first search result to Stackoverflow, you will see something like below after the link is opened. The searched text is highlighted and the page automatically scrolls to the position where the search text ap...

   GOOGLE SEARCH,FEATURED SNIPPET,TECH NEWS     2020-06-13 06:09:38

  Why exception would be thrown when deleting element while looping through HashMap in Java

HashMap and other Collection types are frequently used in Java application programming. This post will explain why exception would be thrown when deleting element with Map.remove() while looping through a Map using Iterator. This issue would also occur to other Collection types such as Set, List. Below is a sample code snippet demonstrating the exception thrown. Map<String,String> map = Collections.synchronizedMap(new TreeMap<String,String>()); map.put("key1","value1"); map.put("ke...

   JAVA,HASHMAP,CONCURRENTMODIFICATIONEXCEPTION     2018-06-30 12:49:09

  Signature sign/verification demo in Java

Digital signature is commonly used in areas where data authentication and integrity are required. It is extremely important to have signature while transferring sensitive data from one peer to other peers through network since there might be malicious applications or man-in-the-middle attacks which may alter the data along the way. Java provides some APIs to generate and verify digital signature. One important class is Signature.  When generating the signature, a private key needs to be pa...

   SECURITY,JAVA,SIGNATURE     2015-11-21 09:48:12

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