Tutorial by Examples: t

Operations that return NaN

Mathematical operations on values other than numbers return NaN. "a" + 1 "b" * 3 "cde" - "e" [1, 2, 3] * 2 An exception: Single-number arrays. [2] * [3] // Returns 6 Also, remember that the + operator concatenates strings. "a" + "b&...

JavaScript • Built-in Constants

Math library functions that return NaN

Generally, Math functions that are given non-numeric arguments will return NaN. Math.floor("a") The square root of a negative number returns NaN, because Math.sqrt does not support imaginary or complex numbers. Math.sqrt(-1)

JavaScript • Built-in Constants

Testing for NaN using isNaN()

window.isNaN() The global function isNaN() can be used to check if a certain value or expression evaluates to NaN. This function (in short) first checks if the value is a number, if not tries to convert it (*), and then checks if the resulting value is NaN. For this reason, this testing method may ...

JavaScript • Built-in Constants

Blocks as Method Parameters

- (void)methodWithBlock:(returnType (^)(paramType1, paramType2, ...))name;

Objective-C Language • Blocks

Join lists

Following ways can be used for joining lists without modifying source list(s). First approach. Has more lines but easy to understand List<String> newList = new ArrayList<String>(); newList.addAll(listOne); newList.addAll(listTwo); Second approach. Has one less line but less readab...

Java Language • Collections

Comparing Objects

In order to compare the equality of custom classes, you can override == and != by defining __eq__ and __ne__ methods. You can also override __lt__ (<), __le__ (<=), __gt__ (>), and __ge__ (>). Note that you only need to override two comparison methods, and Python can handle the rest (== ...

Python Language • Comparisons

Basic usage getting content between buffers and clearing

Output buffering allows you to store any textual content (Text, HTML) in a variable and send to the browser as one piece at the end of your script. By default, php sends your content as it interprets it. <?php // Turn on output buffering ob_start(); // Print some output to the buffer (via...

PHP • Output Buffering

Nested output buffers

You can nest output buffers and fetch the level for them to provide different content using the ob_get_level() function. <?php $i = 1; $output = null; while( $i <= 5 ) { // Each loop, creates a new output buffering `level` ob_start(); print "Current nest level: &quo...

PHP • Output Buffering

Capturing the output buffer to re-use later

In this example, we have an array containing some data. We capture the output buffer in $items_li_html and use it twice in the page. <?php // Start capturing the output ob_start(); $items = ['Home', 'Blog', 'FAQ', 'Contact']; foreach($items as $item): // Note we're about to step &q...

PHP • Output Buffering

Running output buffer before any content

ob_start(); $user_count = 0; foreach( $users as $user ) { if( $user['access'] != 7 ) { continue; } ?> <li class="users user-<?php echo $user['id']; ?>"> <a href="<?php echo $user['link']; ?>"> <?php echo $user...

PHP • Output Buffering

Using Output buffer to store contents in a file, useful for reports, invoices etc

<?php ob_start(); ?> <html> <head> <title>Example invoice</title> </head> <body> <h1>Invoice #0000</h1> <h2>Cost: &pound;15,000</h2> ... </body> </html> <?php...

PHP • Output Buffering

Using the multiprocessing module to parallelise tasks

import multiprocessing def fib(n): """computing the Fibonacci in an inefficient way was chosen to slow down the CPU.""" if n <= 2: return 1 else: return fib(n-1)+fib(n-2) p = multiprocessing.Pool() print(p.map(fib,[38,37,3...

Python Language • Parallel computation

Ignore files that have already been committed to a Git repository

If you have already added a file to your Git repository and now want to stop tracking it (so that it won't be present in future commits), you can remove it from the index: git rm --cached <file> This will remove the file from the repository and prevent further changes from being tracked by...

Git • Ignoring Files and Folders

Basics of multithreading

Using the threading module, a new thread of execution may be started by creating a new threading.Thread and assigning it a function to execute: import threading def foo(): print "Hello threading!" my_thread = threading.Thread(target=foo) The target parameter references the fun...

Python Language • Multithreading

Quoting

By adding > in front of a line, you can create quoted text! > I am a quote I am a quote!

Markdown • Quotes

Recorded (not live) Video Player

twitch • Interactive Embed Video Player

Introduction to WordPress

WordPress [WP] is an open source Content Management System for building apps, websites, and blogs. WP is written in PHP and uses MySQL as the data store for the user content and configuration. It has a rich ecosystem of plugins and themes and enjoys a vibrant open source community, good documentatio...

WordPress • Getting started with WordPress

Creating a hello-world.js module

Node provides the module.exports interface to expose functions and variables to other files. The most simple way to do so is to export only one object (function or variable), as shown in the first example. hello-world.js module.exports = function(subject) { console.log('Hello ' + subject); }...

Node.js • Exporting and Consuming Modules

Limit and Offset relationship

Considering the following users table: idusername1User12User23User34User45User5 In order to constrain the number of rows in the result set of a SELECT query, the LIMIT clause can be used together with one or two positive integers as arguments (zero included). LIMIT clause with one argument When ...

MySQL • Limit and Offset

Italic

Italics can be created by surrounding text with either asterisks or with underscores: *Italicized text* _Also italicized_ Result: Italicized text Also italicized

Markdown • Text Formatting