Tutorial by Examples: a

Hexadecimal Value

Background CSS colors may also be represented as a hex triplet, where the members represent the red, green and blue components of a color. Each of these values represents a number in the range of 00 to FF, or 0 to 255 in decimal notation. Uppercase and/or lowercase Hexidecimal values may be used (i...

CSS • Colors

rgb() Notation

RGB is an additive color model which represents colors as mixtures of red, green, and blue light. In essence, the RGB representation is the decimal equivalent of the Hexadecimal Notation. In Hexadecimal each number ranges from 00-FF which is equivalent to 0-255 in decimal and 0%-100% in percentages....

CSS • Colors

hsl() Notation

HSL stands for hue ("which color"), saturation ("how much color") and lightness ("how much white"). Hue is represented as an angle from 0° to 360° (without units), while saturation and lightness are represented as percentages. p { color: hsl(240, 100%, 50%); /* B...

CSS • Colors

What is the Box Model?

The Edges The browser creates a rectangle for each element in the HTML document. The Box Model describes how the padding, border, and margin are added to the content to create this rectangle. Diagram from CSS2.2 Working Draft The perimeter of each of the four areas is called an edge. Each edge ...

CSS • The Box Model

"Promisifying" functions with callbacks

Given a function that accepts a Node-style callback, fooFn(options, function callback(err, result) { ... }); you can promisify it (convert it to a promise-based function) like this: function promiseFooFn(options) { return new Promise((resolve, reject) => fooFn(options, (err, re...

JavaScript • Promises

Abstract equality / inequality and type conversion

The Problem The abstract equality and inequality operators (== and !=) convert their operands if the operand types do not match. This type coercion is a common source of confusion about the results of these operators, in particular, these operators aren't always transitive as one would expect. &...

JavaScript • Comparison Operations

Using the @property decorator

The @property decorator can be used to define methods in a class which act like attributes. One example where this can be useful is when exposing information which may require an initial (expensive) lookup and simple retrieval thereafter. Given some module foobar.py: class Foo(object): def __...

Python Language • Property Objects

Handling InterruptedException

InterruptedException is a confusing beast - it shows up in seemingly innocuous methods like Thread.sleep(), but handling it incorrectly leads to hard-to-manage code that behaves poorly in concurrent environments. At its most basic, if an InterruptedException is caught it means someone, somewhere, c...

Java Language • Exceptions and exception handling

Using the @property decorator for read-write properties

If you want to use @property to implement custom behavior for setting and getting, use this pattern: class Cash(object): def __init__(self, value): self.value = value @property def formatted(self): return '${:.2f}'.format(self.value) @formatted.setter def ...

Python Language • Property Objects

Showcasing all common Angular constructs

The following example shows common AngularJS constructs in one file: <!DOCTYPE html> <html ng-app="myDemoApp"> <head> <style>.started { background: gold; }</style> <script src="https://code.angularjs.org/1.5.8/angular.min.js">&lt...

AngularJS • Getting started with AngularJS

Link that runs JavaScript

Simply use the javascript: protocol to run the text as JavaScript instead of opening it as a normal link: <a href="javascript:myFunction();">Run Code</a> You can also achieve the same thing using the onclick attribute: <a href="#" onclick="myFunction(); r...

HTML • Anchors and Hyperlinks

Adding the total rows selected to every row

SELECT your_columns, COUNT(*) OVER() as Ttl_Rows FROM your_data_set idnameTtl_Rows1example52foo53bar54baz55quux5 Instead of using two queries to get a count then the line, you can use an aggregate as a window function and use the full result set as the window. This can be used as a base for fur...

SQL • Window Functions

Setting up a flag if other rows have a common property

Let's say I have this data: Table items idnametag1exampleunique_tag2foosimple42barsimple3bazhello51quuxworld I'd like to get all those lines and know if a tag is used by other lines SELECT id, name, tag, COUNT(*) OVER (PARTITION BY tag) > 1 AS flag FROM items The result will be: idnametag...

SQL • Window Functions

Getting a running total

Given this data: dateamount2016-03-122002016-03-11-502016-03-141002016-03-151002016-03-10-250 SELECT date, amount, SUM(amount) OVER (ORDER BY date ASC) AS running FROM operations ORDER BY date ASC will give you dateamountrunning2016-03-10-250-2502016-03-11-50-3002016-03-12200-1002016-03-1410...

SQL • Window Functions

List of true and false values

use feature qw( say ); # Numbers are true if they're not equal to 0. say 0 ? 'true' : 'false'; # false say 1 ? 'true' : 'false'; # true say 2 ? 'true' : 'false'; # true say -1 ? 'true' : 'false'; # true say 1-1 ? 'true' : 'false'; # fa...

Perl Language • True and false

Breakpoints

Breakpoints pause your program once execution reaches a certain point. You can then step through the program line by line, observing its execution and inspecting the contents of your variables. There are three ways of creating breakpoints. From code, using the debugger; statement. From the brow...

JavaScript • Debugging

Basic use and chaining

The pipe operator, %>%, is used to insert an argument into a function. It is not a base feature of the language and can only be used after attaching a package that provides it, such as magrittr. The pipe operator takes the left-hand side (LHS) of the pipe and uses it as the first argument of the ...

R Language • Pipe operators (%>% and others)

Installation

QML comes with newer Version of the cross-platform application framework Qt. You can find the newest Version of Qt in the Downloads section. To create a new QML Project in the Qt Creator IDE, select "File -> New ..." and under "Applications" select "Qt Quick-Application...

qml • Getting started with qml

Check if a string matches a regular expression

3.0 Check if a string consists in exactly 8 digits: $ date=20150624 $ [[ $date =~ ^[0-9]{8}$ ]] && echo "yes" || echo "no" yes $ date=hello $ [[ $date =~ ^[0-9]{8}$ ]] && echo "yes" || echo "no" no

Bash • Pattern matching and regular expressions

Merging, combine and composing Maps

Use putAll to put every member of one map into another. Keys already present in the map will have their corresponding values overwritten. Map<String, Integer> numbers = new HashMap<>(); numbers.put("One", 1) numbers.put("Three", 3) Map<String, Integer> othe...

Java Language • Maps