Tutorial by Examples: re

The removeEventListener() method removes event handlers that have been attached with the addEventListener() method: element.removeEventListener("mousemove", myFunction); Everything (eventname, function, and options) in the removeEventListener must match the one set when adding the even...

A hash in Ruby is an object that implements a hash table, mapping keys to values. Ruby supports a specific literal syntax for defining hashes using {}: my_hash = {} # an empty hash grades = { 'Mark' => 15, 'Jimmy' => 10, 'Jack' => 10 } A hash can also be created using the standard new...

You can use slices to very easily reverse a str, list, or tuple (or basically any collection object that implements slicing with the step parameter). Here is an example of reversing a string, although this applies equally to the other types listed above: s = 'reverse me!' s[::-1] # '!em esrever...

It's possible to create generator iterators using a comprehension-like syntax. generator = (i * 2 for i in range(3)) next(generator) # 0 next(generator) # 2 next(generator) # 4 next(generator) # raises StopIteration If a function doesn't necessarily need to be passed a list, you can sa...

When you clone a repository that uses submodules, you'll need to initialize and update them. $ git clone --recursive https://github.com/username/repo.git This will clone the referenced submodules and place them in the appropriate folders (including submodules within submodules). This is equivale...

Routes are defined in config/routes.rb. They are often defined as a group of related routes, using the resources or resource methods. resources :users creates the following seven routes, all mapping to actions of UsersController: get '/users', to: 'users#index' post '/users', ...

Syntax : history.replaceState(data, title [, url ]) This method modifies the current history entry instead of creating a new one. Mainly used when we want to update URL of the current history entry. window.history.replaceState("http://example.ca", "Sample Title", "/exam...

With a Frame When you know the exact dimensions you want to set for your label, you can initialize a UILabel with a CGRect frame. Swift let frame = CGRect(x: 0, y: 0, width: 200, height: 21) let label = UILabel(frame: frame) view.addSubview(label) Objective-C CGRect frame = CGRectMake(0, 0,...

Use new Date() to generate a new Date object containing the current date and time. Note that Date() called without arguments is equivalent to new Date(Date.now()). Once you have a date object, you can apply any of the several available methods to extract its properties (e.g. getFullYear() to get t...

Jsoup can be used to extract links and email address from a webpage, thus "Web email address collector bot" First, this code uses a Regular expression to extract the email addresses, and then uses methods provided by Jsoup to extract the URLs of links on the page. public class JSoupTest {...

The attribute tools:ignore can be used in xml files to dismiss lint warnings. BUT dismissing lint warnings with this technique is most of the time the wrong way to proceed. A lint warning must be understood and fixed... it can be ignored if and only if you have a full understanding of it's meaning...

def multiply(s1, s2): print('{arg1} * {arg2} = {res}'.format(arg1=s1, arg2=s2, res=s1*s2)) return s1 * s2 asequence = [1, 2, 3] Given an initializer the function is started by applying it to the...

# First falsy element or last element if all are truthy: reduce(lambda i, j: i and j, [100, [], 20, 10]) # = [] reduce(lambda i, j: i and j, [100, 50, 20, 10]) # = 10 # First truthy element or last element if all falsy: reduce(lambda i, j: i or j, [100, [], 20, 0]) # = 100 reduce(la...

Presence works by sending messages when a user joins, leaves, or times out from a particular channel. You can listen for these messages to track who is in a channel, and how long since they did anything. First, make sure each user as a UUID. Set this when you initialize PubNub: var pubnub = PUBNUB...

In addition to .done, .fail and .always promise callbacks, which are triggered based on whether the request was successful or not, there is the option to trigger a function when a specific HTTP Status Code is returned from the server. This can be done using the statusCode parameter. $.ajax({ t...

For example calculating the average of each i-th element of multiple iterables: def average(*args): return float(sum(args)) / len(args) # cast to float - only mandatory for python 2.x measurement1 = [100, 111, 99, 97] measurement2 = [102, 117, 91, 102] measurement3 = [104, 102, 95, 101] ...

Extensions are used to extend the functionality of existing types in Swift. Extensions can add subscripts, functions, initializers, and computed properties. They can also make types conform to protocols. Suppose you want to be able to compute the factorial of an Int. You can add a computed property...

CREATE INDEX ix_cars_employee_id ON Cars (EmployeeId); This will create an index for the column EmployeeId in the table Cars. This index will improve the speed of queries asking the server to sort or select by values in EmployeeId, such as the following: SELECT * FROM Cars WHERE EmployeeId = 1 ...

A basic Employees table, containing an ID, and the employee's first and last name along with their phone number can be created using CREATE TABLE Employees( Id int identity(1,1) primary key not null, FName varchar(20) not null, LName varchar(20) not null, PhoneNumber varchar(10)...

Sometimes the number of types you are mapping exceeds the 7 provided by the Func<> that does the construction. Instead of using the Query<> with the generic type argument inputs, we will provide the types to map to as an array, followed by the mapping function. Other than the initial ma...