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  Load and execute JavaScript

When we load and execute JavaScript in a webpage, there are many points we need to care about because of its design and feature. There are two features about JavaScript execution in a browser: 1). The JavaScript codes will be executed immediately once loaded;2). When JavaScript codes are being executed, they will block the following contents (including page rendering and other resources downloading). So if there are multiple js files to be loaded, these codes will be executed sequentially. Since...

   JavaScript,async,defer,load,execute     2013-06-07 04:53:46

  The evolving history of asynchronous operation in JavaScript

JavaScript is single threaded, it means there would be only one task running at any point of time. But this would slow down the overall program execution if there is long running task, hence asynchronous task execution is desired in complex cases. To achieve asynchronous task execution, there are a few options introduced in JavaScript. setTimeout/setInterval Event Promise Async/Await setTimeout/setInterval is one of the first mechanisms introduced in JavaScript to simulate asynchronous operati...

   JAVASCRIPT,ASYNC,PROMISE,AWAIT     2019-11-09 08:21:56

  JavaScript: Private variables

The first thing you often hear when talking about JavaScript is often “JavaScript doesn’t have visibility modifiers, hence it doesn’t support private variables”. This is only valid for 50%, because JavaScript indeed doesn’t have visibility modifiers (public, private, friend) but it has closures and function scopes. With these tools we can make variables private. Let’s take the following function: var names = ["Kenneth", "John", "Marc", "Robert"]; var lookup =...

   JavaScript,private variable,closure     2012-04-28 11:46:34

  4 asynchronous programming methods in JavaScript

You may know the execution environment of JavaScript is single threaded. The so called single thread means only one task can be running at any time, if there are many tasks, they need to be in a queue and wait for the previous task to be completed. The advantage of this mode is it's easy to implement and the execution environment is relative simple; the disadvantage is that if one task takes long time, the tasks following it must wait in the queue and this will delay other tasks consequently. Th...

   JAVASCRIPT,ASYNCHRONOUS PROGRAMMING, EVENT MODEL,PROMISE     2012-12-25 00:55:47

  Parallel Javascript

Lately the ideas for a parallel, shared memory JavaScript have begun to take shape. I’ve been discussing with various JavaScript luminaries and it seems like a design is starting to emerge. This post serves as a documentation of the basic ideas; I’m sure the details will change as we go along. User Model The model is that a JavaScript worker (the “parent”) may spawn a number of child tasks (the “children”). The parent is suspended while the children exe...

   Parallel JavaScript,API,Spawn,Parent,Task     2012-01-11 12:02:00

  A possible way to recover deleted files on Linux

Last week I was generating a MD5 sum for an virtual machine image on one OpenNebula server: # ls -l test.img -rw-r--r-- 1 root root 10486808576 Oct 12 02:21 test.img # md5sum test.img At the same time I was clearing the files on the server on another terminal and deleted the above image file mistakenly with : # rm test.img Since this image file is 10GB, it took some time to remove this file from the server, so I used the Ctrl+Z command to suspend the remove command. [1]+ Stopped ...

   Linux,File,Recovery     2013-11-26 07:03:37

  try { return } finally {}

Do you know what value will be printed when following program is ran? class Test { public int aaa() { int x = 1; try { return ++x; } catch (Exception e) { } finally { ++x; } return x; } public static void main(String[] args) { Test t = new Test(); int y = t.aaa(); System.out.println(y); } } And before answering the above question, do you have answers to following questions? If ther...

   JAVA,JAVA INTERVIEW QUESTION     2016-09-26 08:06:28

  A trap in PDOStatement::bindParam

First, let's check out below codes: <?php $dbh = new PDO('mysql:host=localhost;dbname=test', "test"); $query = <<prepare($query); $bind_params = array(':username' => "laruence", ':password' => "weibo"); foreach( $bind_params as $key => $value ){ $statement->bindParam($key, $value); } $statement->execute(); What is the SQL executed finally? Is there any problem with above codes? Many people may think the query executed is : INSERT INTO `user` (`username`, `password...

   PHP,Trap,bindParam     2013-08-29 10:48:55

  PHP to output string to client terminal

It is a common task to echo messages to the user using PHP. There are lots of ways where the message can be echoed to the client terminal(browser or console window) through PHP. These includes some well know debug methods like var_dump() and var_export() etc. In this post, we will show you some other methods shared by Laruence, one of the core members of PHP development team. 1. echo First comes with the most common one : echo. $str = "Hello PHP\n"; echo $str; 2. print Then comes another c...

   TRICKS,DEBUG,OUTPUT,PHP     2015-10-01 03:16:56

  How to commit code to OpenStack

If you want to make contributions to OpenStack, the best way to start is to help the community with blueprint or submit bug fix. To commit codes, you need to conform to some rules in the community. Work flow Register an OpenID Apply for a CLA certificate Apply for company CLA certificate Update contributor list Join OpenStack Contributors group and OpenStack group Set up SSH Keys Get a blueprint/bug git clone codes to local disk. Configure user name and user email and openid Modify codes in a l...

   OpenStack,Contribution     2013-08-04 23:04:45

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