Tutorial by Examples: re

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

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

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

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

Numbered lists

1. Lists 2. Can be 3. Numbered Lists Can be Numbered Note that the numbers themselves are ignored: 1. This is the first item 5. This is the fifth item 7. This is the seventh item This is the first item This is the fifth item This is the seventh item However, the firs...

Markdown • Creating Lists

Precondition and Postcondition

One use case for assertion is precondition and postcondition. This can be very useful to maintain invariant and design by contract. For a example a length is always zero or positive so this function must return a zero or positive value. #include <stdio.h> /* Uncomment to disable `assert()`...

C Language • Assertion

Making a Payment with a Vaulted Credit Card (Node)

In this example, we'll be looking at how to store a credit card using the PayPal vault, then reference that stored credit card to process a credit card transaction for a user. The reason why we would want to use the vault is so that we don't have to store sensitive credit card information on our ow...

PayPal • Making a Credit Card Payment (Node)

Creating and reading stacktraces

When an exception object is created (i.e. when you new it), the Throwable constructor captures information about the context in which the exception was created. Later on, this information can be output in the form of a stacktrace, which can be used to help diagnose the problem that caused the excep...

Java Language • Exceptions and exception handling

Convert formatted string representation of date to Date object

This method can be used to convert a formatted string representation of a date into a Date object. /** * Parses the date using the given format. * * @param formattedDate the formatted date string * @param dateFormat the date format which was used to create the string. ...

Java Language • Date Class

Searching for a file by name or extension

To find files/directories with a specific name, relative to pwd: $ find . -name "myFile.txt" ./myFile.txt To find files/directories with a specific extension, use a wildcard: $ find . -name "*.txt" ./myFile.txt ./myFile2.txt To find files/directories matching one of ma...

Bash • Find

What is a lambda expression?

A lambda expression provides a concise way to create simple function objects. A lambda expression is a prvalue whose result object is called closure object, which behaves like a function object. The name 'lambda expression' originates from lambda calculus, which is a mathematical formalism invented...

C++ • Lambdas

Specifying the return type

For lambdas with a single return statement, or multiple return statements whose expressions are of the same type, the compiler can deduce the return type: // Returns bool, because "value > 10" is a comparison which yields a Boolean result auto l = [](int value) { return value &gt...

C++ • Lambdas

Capture by value

If you specify the variable's name in the capture list, the lambda will capture it by value. This means that the generated closure type for the lambda stores a copy of the variable. This also requires that the variable's type be copy-constructible: int a = 0; [a]() { return a; // Ok, 'a' ...

C++ • Lambdas

What are Tuples?

Tuples group multiple values into a single compound value. The values within a tuple can be of any type and do not have to be of the same type as each other. Tuples are created by grouping any amount of values: let tuple = ("one", 2, "three") // Values are read using index n...

Swift Language • Tuples