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  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

  Top 7 M-Commerce Trends to Pay Attention in 2018

Ever since eCommerce came to mobile, new technologies have been providing an advanced shopping experience to the users. Every year new concepts are introducing in the industry to improve the ways users are shopping through smartphones, tablets, and other mobile devices. Pieces of evidence advocate that more than 80% of buyers prefer using smartphones than computers to search products, compare prices and, locate stores. According to Statista, m-commerce revenue is forecasted to reach $669 b...

   MOBILE APP, APP DEVELOPMENT,MCOMMERCE,BUSINESS OWNERS     2018-03-23 07:44:11

  Extension context menu is missing in Firefox after restart

If you have experience of writing Chrome extension, you may be familiar with how you can add a context menu for your extension. The code would be similar to below: chrome.runtime.onInstalled.addListener(function() { chrome.contextMenus.removeAll(); chrome.contextMenus.create({ "id": "your_id", "title": "Your Title", "contexts": ["all"] }); }); You need to add a listener listening to the extension install event. Once the extension is installed, create a contex...

   CHROME,FIREFOX,EXTENSION,CONTEXT MENU     2018-11-16 20:58:20

  Ruby net-scp cannot scp multiple files with asterisk(*)

net-ssh/net-scp is a Ruby gem which can be used to scp files between different *nix machines. It's similar to how the *nix scp command. It can be used to scp a file or a directory. However, it seems it has some problem to scp multiple files using pattern *. For example, below script is supposed to download all files from remote directory to local directory: require 'net/scp' host = 'testmachine' login = 'testaccount' password = "testpassword" remote_path = '/tmp/remote...

   NET-SCP,RUBY,ASTERISK,MULTIPLE FILES     2016-10-20 03:00:13

  8 most successful open source products

Open source itself is a successful product. It is not only liked by many personals, many famous enterprises like itAlthough there are numerous open source projects and open source products, which is the most successful among them? "Success" is defined as the widely used + well known here. In many successful open source products, only a minority leaders. Here we share 8 most successful open source products we think they deserve to be.LinuxReason: Linux + GNU = GNU / Linux. It has been almost 2...

   Open source,MySQL,Linux,BIND,BSD     2012-04-19 08:29:00

  One reason why mcrypt responds slowly

This morning one colleague came over and talked about one script which used mcrypt responded very slowly, the server configurations are fine. But the reason for the slowness is unknown. Here is one script which reproduces the issue: <?php $dmcryptText = "dummy"; $key = "foobar"; $size = mcrypt_get_iv_size(MCRYPT_BLOWFISH,MCRYPT_MODE_ECB); $iv = mcrypt_create_iv($size); //Take care $m = mcrypt_ecb(MCRYPT_BLOWFISH, $key, $dmcryptText, MCRYPT_DECRYPT, $iv); var_dump($m); When 20 requests of&...

   SOLUTION,SLOW,MCRYPT,RESPONSE,PHP     2012-09-27 12:03:16

  Integer overflow

You may be familiar with integer overflow, but what you may not be familiar with is how gcc handles signed integer overflow. First let's look at the standard, for unsigned integer, the standard says : A computation involving unsigned operands can never overflow, because a result that cannot be represented by the resulting unsigned integer type is reduced modulo the number that is one greater than the largest value that can be represented by the resulting type. In other words, unsigned integer ov...

   Integer overflow,gcc,Linux     2012-10-20 13:33:10

  When will resizing be triggered in Java HashMap?

HashMap is one of the most frequently used collection types in Java, it stores key-value pairs. Ideally it expects to use hash table which expects the data access time complexity to be O(1), however, due to hash conflicts, in reality, it uses linked list or red-black tree to store data which makes the worst case time complexity to be O(logn).  Although collections are using data structures like arrays and linked lists, unlike arrays, they will dynamically resize when there is not enough spa...

   JAVA,RESIZE,HASHMAP,THRESHOLD     2020-05-02 20:41:19

  An alternative way to parse URL in JavaScript

Normally when we need to process URL in JavaScript, we may use the location object. Then we can use location.hostname,location.href,location.port etc to get the information we need. In this post, we will parse an URL with an alternative way. We can use an URL to create a DOM object by calling document.createElement("a"). The complete code is: function parseURL(url) { var a = document.createElement('a'); a.href = url; return { source: url, protocol: a.protocol.replace(':',''), host: a.ho...

   URL,location,parse     2014-03-03 07:05:11

  Memory related exception analysis in Java

Java Virtual Machine Specification divides the memory of JVM into several areas : Heap, Stack, The Program Counter register and Method area etc. In HotSpot JVM, heap is composed of Young, Tenured and Perm. There are different OutOfMemory error can happen in different memory area. Next is an overview of some of these OOM errors. StackOverflowError The JVM will allow only a specified number of stacks created nested. An JVM option -Xss can be set to determine the maximum stack size. If the num...

   Java, Memory model, Memory exception, OOM     2015-01-19 06:54:27

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