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Standard array initialization

There are many ways to create arrays. The most common are to use array literals, or the Array constructor: var arr = [1, 2, 3, 4]; var arr2 = new Array(1, 2, 3, 4); If the Array constructor is used with no arguments, an empty array is created. var arr3 = new Array(); results in: [] Note...

JavaScript • Arrays

Introduction

In JavaScript, functions may be anonymously defined using the "arrow" (=>) syntax, which is sometimes referred to as a lambda expression due to Common Lisp similarities. The simplest form of an arrow function has its arguments on the left side of => and the return value on the right...

JavaScript • Arrow Functions

HTML output from web server

PHP can be used to add content to HTML files. While HTML is processed directly by a web browser, PHP scripts are executed by a web server and the resulting HTML is sent to the browser. The following HTML markup contains a PHP statement that will add Hello World! to the output: <!DOCTYPE html&gt...

PHP • Getting started with PHP

Standard function prototype

Start by defining a Foo function that we'll use as a constructor. function Foo (){} By editing Foo.prototype, we can define properties and methods that will be shared by all instances of Foo. Foo.prototype.bar = function() { return 'I am bar'; }; We can then create an instance using the ...

JavaScript • Inheritance

Anonymous Function

Defining an Anonymous Function When a function is defined, you often give it a name and then invoke it using that name, like so: foo(); function foo(){ // ... } When you define a function this way, the Javascript runtime stores your function in memory and then creates a reference to th...

JavaScript • Functions

Using GET and no parameters

var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function () { if (xhttp.readyState === XMLHttpRequest.DONE && xhttp.status === 200) { //parse the response in xhttp.responseText; } }; xhttp.open("GET", "ajax_info.txt", true); xhttp.send(...

JavaScript • AJAX

echo and print

echo and print are language constructs, not functions. This means that they don't require parentheses around the argument like a function does (although one can always add parentheses around almost any PHP expression and thus echo("test") won't do any harm either). They output the string r...

PHP • Outputting the Value of a Variable

Difference between Object.key and Object.prototype.key

Unlike in languages like Python, static properties of the constructor function are not inherited to instances. Instances only inherit from their prototype, which inherits from the parent type's prototype. Static properties are never inherited. function Foo() {}; Foo.style = 'bold'; var foo = ne...

JavaScript • Inheritance

Object.keys

5 Object.keys(obj) returns an array of a given object's keys. var obj = { a: "hello", b: "this is", c: "javascript!" }; var keys = Object.keys(obj); console.log(keys); // ["a", "b", "c"]

JavaScript • Objects

List Comprehensions

A list comprehension creates a new list by applying an expression to each element of an iterable. The most basic form is: [ <expression> for <element> in <iterable> ] There's also an optional 'if' condition: [ <expression> for <element> in <iterable> if <c...

Python Language • List comprehensions

Dictionary Comprehensions

A dictionary comprehension is similar to a list comprehension except that it produces a dictionary object instead of a list. A basic example: Python 2.x2.7 {x: x * x for x in (1, 2, 3, 4)} # Out: {1: 1, 2: 4, 3: 9, 4: 16} which is just another way of writing: dict((x, x * x) for x in (1, 2...

Python Language • List comprehensions

Generator Expressions

Generator expressions are very similar to list comprehensions. The main difference is that it does not create a full set of results at once; it creates a generator object which can then be iterated over. For instance, see the difference in the following code: # list comprehension [x**2 for x in r...

Python Language • List comprehensions

Class Constructor

The fundamental part of most classes is its constructor, which sets up each instance's initial state and handles any parameters that were passed when calling new. It's defined in a class block as though you're defining a method named constructor, though it's actually handled as a special case. cla...

JavaScript • Classes

Set Comprehensions

Set comprehension is similar to list and dictionary comprehension, but it produces a set, which is an unordered collection of unique elements. Python 2.x2.7 # A set containing every value in range(5): {x for x in range(5)} # Out: {0, 1, 2, 3, 4} # A set of even numbers between 1 and 10: {x f...

Python Language • List comprehensions

Hello World

This program will output "Hello World!" #import <Foundation/Foundation.h> int main(int argc, char * argv[]) { NSLog(@"Hello World!"); } #import is a pre-processor directive, which indicates we want to import or include the information from that file into the pr...

Objective-C Language • Getting started with Objective-C Language

Starting a Project

Django is a web development framework based on Python. Django 1.11 (the latest stable release) requires Python 2.7, 3.4, 3.5 or 3.6 to be installed. Assuming pip is available, installation is as simple as running the following command. Keep in mind, omitting the version as shown below will install t...

Django • Getting started with Django

Basic use of map, itertools.imap and future_builtins.map

The map function is the simplest one among Python built-ins used for functional programming. map() applies a specified function to each element in an iterable: names = ['Fred', 'Wilma', 'Barney'] Python 3.x3.0 map(len, names) # map in Python 3.x is a class; its instances are iterable # Out: &...

Python Language • Map Function

Basic use of filter

To filter discards elements of a sequence based on some criteria: names = ['Fred', 'Wilma', 'Barney'] def long_name(name): return len(name) > 5 Python 2.x2.0 filter(long_name, names) # Out: ['Barney'] [name for name in names if len(name) > 5] # equivalent list comprehension #...

Python Language • Filter

Your first Swift program

Write your code in a file named hello.swift: print("Hello, world!") To compile and run a script in one step, use swift from the terminal (in a directory where this file is located): To launch a terminal, press CTRL+ALT+T on Linux, or find it in Launchpad on macOS. To change dire...

Swift Language • Getting started with Swift Language

Non-HTML output from web server

In some cases, when working with a web server, overriding the web server's default content type may be required. There may be cases where you need to send data as plain text, JSON, or XML, for example. The header() function can send a raw HTTP header. You can add the Content-Type header to notify t...

PHP • Getting started with PHP