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This example assumes Ruby and Ruby on Rails have already been installed properly. If not, you can find how to do it here. Open up a command line or terminal. To generate a new rails application, use rails new command followed by the name of your application: $ rails new my_app If you want to c...

Logical OR (||), reading left to right, will evaluate to the first truthy value. If no truthy value is found, the last value is returned. var a = 'hello' || ''; // a = 'hello' var b = '' || []; // b = [] var c = '' || undefined; // c = undefined var d = 1 |...

Standard usage for (var i = 0; i < 100; i++) { console.log(i); } Expected output: 0 1 ... 99 Multiple declarations Commonly used to cache the length of an array. var array = ['a', 'b', 'c']; for (var i = 0; i < array.length; i++) { console.log(array[i]); } Expect...

Breaking out of a while loop var i = 0; while(true) { i++; if(i === 42) { break; } } console.log(i); Expected output: 42 Breaking out of a for loop var i; for(i = 0; i < 100; i++) { if(i === 42) { break; } } console.log(i); Expected o...

Continuing a "for" Loop When you put the continue keyword in a for loop, execution jumps to the update expression (i++ in the example): for (var i = 0; i < 3; i++) { if (i === 1) { continue; } console.log(i); } Expected output: 0 2 Continuing a While...

Using the def statement is the most common way to define a function in python. This statement is a so called single clause compound statement with the following syntax: def function_name(parameters): statement(s) function_name is known as the identifier of the function. Since a function def...

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 augment the behavior of other functions or methods. Any function that takes a function as a parameter and returns an augmented function can be used as a decorator. # This simplest decorator does nothing to the function being decorated. Such # minimal decorators can occasionally be used ...

As mentioned in the introduction, a decorator is a function that can be applied to another function to augment its behavior. The syntactic sugar is equivalent to the following: my_func = decorator(my_func). But what if the decorator was instead a class? The syntax would still work, except that now m...

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...

A decorator takes just one argument: the function to be decorated. There is no way to pass other arguments. But additional arguments are often desired. The trick is then to make a function which takes arbitrary arguments and returns a decorator. Decorator functions def decoratorfactory(message): ...

The math module contains the math.sqrt()-function that can compute the square root of any number (that can be converted to a float) and the result will always be a float: import math math.sqrt(9) # 3.0 math.sqrt(11.11) # 3.3331666624997918 math.sqrt(Decimal('6.25')) ...

Sometimes you don't want to have your function accessible/stored as a variable. You can create an Immediately Invoked Function Expression (IIFE for short). These are essentially self-executing anonymous functions. They have access to the surrounding scope, but the function itself and any internal va...

The then method of a promise returns a new promise. const promise = new Promise(resolve => setTimeout(resolve, 5000)); promise // 5 seconds later .then(() => 2) // returning a value from a then callback will cause // the new promise to resolve with this value .then...

The setTimeout() method calls a function or evaluates an expression after a specified number of milliseconds. It is also a trivial way to achieve an asynchronous operation. In this example calling the wait function resolves the promise after the time specified as first argument: function wait(ms) ...

A traditional for-loop A traditional for loop has three components: The initialization: executed before the look block is executed the first time The condition: checks a condition every time before the loop block is executed, and quits the loop if false The afterthought: performed every time a...

import random shuffle() You can use random.shuffle() to mix up/randomize the items in a mutable and indexable sequence. For example a list: laughs = ["Hi", "Ho", "He"] random.shuffle(laughs) # Shuffles in-place! Don't do: laughs = random.shuffle(laughs) p...

import random randint() Returns a random integer between x and y (inclusive): random.randint(x, y) For example getting a random number between 1 and 8: random.randint(1, 8) # Out: 8 randrange() random.randrange has the same syntax as range and unlike random.randint, the last value is no...

jQuery is the starting point for writing any jQuery code. It can be used as a function jQuery(...) or a variable jQuery.foo. $ is an alias for jQuery and the two can usually be interchanged for each other (except where jQuery.noConflict(); has been used - see Avoiding namespace collisions). Assumi...

git log will display all your commits with the author and hash. This will be shown over multiple lines per commit. (If you wish to show a single line per commit, look at onelineing). Use the q key to exit the log. By default, with no arguments, git log lists the commits made in that reposito...