Overview
In this example 2 clients send information to each other through a server. One client sends the server a number which is relayed to the second client. The second client halves the number and sends it back to the first client through the server. The first client does the same. The server st...
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...
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...
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...
All angles below are in radians. An angle r in radians has measure 180 * r / Math.PI in degrees.
Sine
Math.sin(r);
This will return the sine of r, a value between -1 and 1.
Math.asin(r);
This will return the arcsine (the reverse of the sine) of r.
Math.asinh(r)
This will return the hype...
The exit construct can be used to pass a return code to the executing environment.
#!/usr/bin/php
if ($argv[1] === "bad") {
exit(1);
} else {
exit(0);
}
By default an exit code of 0 will be returned if none is provided, i.e. exit is the same as exit(0). As exit is not a ...
Place this code in a file named HelloWorld.scala:
object Hello {
def main(args: Array[String]): Unit = {
println("Hello World!")
}
}
Live demo
To compile it to bytecode that is executable by the JVM:
$ scalac HelloWorld.scala
To run it:
$ scala Hello
When the Scala...
Functions can return a value that you can use directly:
def give_me_five():
return 5
print(give_me_five()) # Print the returned value
# Out: 5
or save the value for later use:
num = give_me_five()
print(num) # Print the saved returned value
# Out: 5
or use the value f...
Decorators normally strip function metadata as they aren't the same. This can cause problems when using meta-programming to dynamically access function metadata. Metadata also includes function's docstrings and its name.
functools.wraps makes the decorated function look like the original function b...
#include <stdio.h>
enum Op
{
ADD = '+',
SUB = '-',
};
/* add: add a and b, return result */
int add(int a, int b)
{
return a + b;
}
/* sub: subtract b from a, return result */
int sub(int a, int b)
{
return a - b;
}
/* getmath: return the appropriate m...
Create a file hello.html with the following content:
<!DOCTYPE html>
<html>
<head>
<title>Hello, World!</title>
</head>
<body>
<div>
<p id="hello">Some random text</p>
</div>
<script src=...
Basic Arithmetic
Return a value that is the result of applying the left hand operand to the right hand operand, using the associated mathematical operation. Normal mathematical rules of commutation apply (i.e. addition and multiplication are commutative, subtraction, division and modulus are not).
...
For every infix operator, e.g. + there is a operator-function (operator.add for +):
1 + 1
# Output: 2
from operator import add
add(1, 1)
# Output: 2
even though the main documentation states that for the arithmetic operators only numerical input is allowed it is possible:
from operator impo...
Instead of this lambda-function that calls the method explicitly:
alist = ['wolf', 'sheep', 'duck']
list(filter(lambda x: x.startswith('d'), alist)) # Keep only elements that start with 'd'
# Output: ['duck']
one could use a operator-function that does the same:
from operator import metho...
Grouping the key-value pairs of a dictionary by the value with itemgetter:
from itertools import groupby
from operator import itemgetter
adict = {'a': 1, 'b': 5, 'c': 1}
dict((i, dict(v)) for i, v in groupby(adict.items(), itemgetter(1)))
# Output: {1: {'a': 1, 'c': 1}, 5: {'b': 5}}
which ...
class MyClass {
func sayHi() { print("Hello") }
deinit { print("Goodbye") }
}
When a closure captures a reference type (a class instance), it holds a strong reference by default:
let closure: () -> Void
do {
let obj = MyClass()
// Captures a strong re...
