Today I Learned

Open VSCode shortcut

Vscode

The shortcut for opening the Visual Studio Code command palette is:

Ctrl/Cmd + Shift + P

Hide VSCode teminal shortcut

Vscode

Hide the terminal with the following shortcut:

Ctrl/Cmd+j

Switch Rails Database

Ruby On Rails

Switch your rails app database without having to touch a single file. Pass --force to skip prompts.

rails db:system:change --to=postgresql

Map()

Javascript

This method is used to create a new Map data structure. A Map is a built-in data structure in JavaScript that allows you to store key-value pairs and provides various methods for working with these pairs. Here's how you can use "new Map()" to create a new Map:

Example:

const myMap = new Map();myMap.set('name', 'John'); 
myMap.set('age', 30);console.log(myMap.get('name')); // Output: 'John' 
console.log(myMap.get('age')); // Output: 30

npm cache verify

NodeJs

This command is useful for ensuring that your local npm cache is in a healthy state, which can help prevent issues when installing or updating packages. If any issues or corruption are detected, npm cache verify will attempt to fix them. It's a maintenance command to help maintain the reliability of your local npm package cache.

Reverse Proxy

A reverse proxy is like a guardian for web servers. It sits between client devices (like browsers) and web servers, accepting requests from clients and directing them to the appropriate server to fulfill those requests. It's a way to balance the load on multiple servers and provide an extra layer of security and performance optimization for websites and web applications.

Operational Direction: A reverse proxy is placed between a client and one or more backend servers. It serves as a gateway for client requests, forwarding those requests to the appropriate backend server or server cluster based on various criteria.
Load Balancing: Reverse proxies are commonly used for load balancing across multiple servers, ensuring even distribution of incoming requests to maintain system performance.
Security and Protection: They provide an additional layer of security by shielding backend servers from direct exposure to the internet. This helps protect servers from direct attacks.

.is_a? method

Ruby

In Ruby, the .is_a? method is used to check if an object is an instance of a particular class or a subclass of that class. It allows you to determine if an object belongs to a certain class in the class hierarchy. The .is_a? method returns true if the object is an instance of the specified class or one of its subclasses, and false otherwise.

Example:

# Define a class 
class Animal 
end# Create an object 
dog = Animal.new# Check if the object is an instance of a class 
puts dog.is_a?(Animal) # true 
puts dog.is_a?(Object) # true, since all objects are instances of Object 
puts dog.is_a?(String) # false, since a dog is not a String

index/_mapping

Elasticsearch

In Elasticsearch, you store your data in indices, which are like containers for your information. Each index can have different kinds of data, like text, numbers, or dates.

Now, think of "mapping" as a set of rules that tells Elasticsearch what kind of data to expect in each index. It's like saying, "In this index, we have names, and they should be stored as text. In that index, we have numbers, and they should be treated as numbers."

So, when you request the _mapping, you're basically asking Elasticsearch to show you the rule book for each index. This rule book describes how data is organized and what type of data each field should contain.

.sub(pattern, replacement)

Ruby

This method is used to replace the first occurrence of a specified pattern.

Example:

text = "Hello, World! This is a test. Hello, Universe!" 
new_text =text.sub("Hello", "Hi") 
puts new_text # => "Hi, World! This is a test. Hello, Universe!"

.method

Ruby

This method is used to retrieve a list of all the public methods available for an object. This method returns an array of symbols, where each symbol represents a method that can be called on the object.

.class

Ruby

This method can be used to know the class of an object, which allows you to inspect and work with the class itself, rather than just the object.

Example:

"Hello".class # => String 
10.class # => Number 
10.0.class # => Float

readonly type

Typescript

The "readonly" modifier is used to indicate that a property or variable should not be modified once it has been initialized. It ensures that the value of the property remains constant throughout the lifetime of the object or variable.

Example with an array:

const numbers: readonly number[] = [1, 2, 3]; 
numbers[0] = 4; // Error! Cannot assign to an element of a readonly array 
numbers.push(4); // Error! Cannot push to a readonly array

.present?

Ruby

This method is the opposite of the .blank? method. It is used to check whether a string, array, or other data structure contains meaningful content, and it returns true if the object is not empty, contains non-whitespace characters, or is not nil. Otherwise, it returns false.

Example:

"".present? # false (empty string) 
" ".present? # false (whitespace characters only) 
nil.present? # false (nil) 
"hello".present? # true (contains non-whitespace characters) 
[1, 2, 3].present? # true (array with elements)

.blank?

Ruby

This method is used to check whether a string, array, or other data structure is empty or contains only whitespace characters.
It returns true if the object is empty contains only whitespace, or is nil. Otherwise, it returns false.

Example:

"".blank? # true (empty string) 
" ".blank? # true (whitespace characters only) 
nil.blank? # true (nil) 
"hello".blank? # false (contains non-whitespace characters) 
[1, 2, 3].blank? # false (array with elements)

Select into statement

Postgres

The "SELECT INTO" statement is used to retrieve data from a database table and store it into variables or a new table.

Example:

-- Assigning Values to Variables 
DECLARE @variable_name data_type; 
SELECT column_name INTO @variable_name FROM table_name WHERE condition;-- Creating a New Table 
SELECT column1, column2 INTO new_table FROM old_table WHERE condition;-- Inserting Data into an Existing Table 
INSERT INTO existing_table (column1, column2) 
SELECT column1, column2 FROM source_table WHERE condition;