Tutorial by Examples: n

Optional<String> optionalWithValue = Optional.of("foo"); optionalWithValue.ifPresent(System.out::println);//Prints "foo". Optional<String> emptyOptional = Optional.empty(); emptyOptional.ifPresent(System.out::println);//Does nothing.

DOM stands for Document Object Model. It is an object-oriented representation of structured documents like XML and HTML. Setting the textContent property of an Element is one way to output text on a web page. For example, consider the following HTML tag: <p id="paragraph"></p&g...

Introduction All modern web browsers, NodeJs as well as almost every other JavaScript environments support writing messages to a console using a suite of logging methods. The most common of these methods is console.log(). In a browser environment, the console.log() function is predominantly used f...

A normal function declaration looks like this: function foo(){ } A function defined like this is accessible from anywhere within its context by its name. But sometimes it can be useful to treat function references like object references. For example, you can assign an object to a variable based...

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...

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...

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 ...

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...

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(...

Python is a widely used high-level programming language for general-purpose programming, created by Guido van Rossum and first released in 1991. Python features a dynamic type system and automatic memory management and supports multiple programming paradigms, including object-oriented, imperative, f...

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...

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...

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...

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...

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...

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...

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...

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...

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: &...

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...