Launch School Notes !

HTTP Describe what HTTP is and the role of the request and the response. HTTP is just a text sent over the internet with a set of rules that governs how computer communicates with each other. It follows a model whereby a client makes a request and then wait for a response from a server. HTTP itself doesn't transmit data, it depends on TCP/IP protocol to get request/response from one machine to another.  What are the components of an HTTP request and an HTTP response? HTTP request and response has a header and body.  HTTP response will contain status code ( 200 OK)  and headers which is a metadata that contain information for content-type (text/html),  Content-Encoding:gzip (type of file compression), server (name of the server), Location (new resource location for redirects) and a HTTP body  HTTP request header contain information on HTTP method (GET/POST) , path and parameter to allow server to know how to find information, along with optional hea...

- within same specificity , the styles further in the bottom take higher precedence, like a water fall cascade. p {     color: red; } p {     color: blue; } The paragraph will be blue. - There are different specificity base on different selector    - ID        1-0-0    - class    0-1-0    - type     0-0-1 ID is the most specific, so its style will take precedence if class and type classed with ID. - You can combine selector , so the highest number will take precedence #num .cili .love {      color: red; } 1-2-0 #num .cili {      color: blue; } 1-1-0 Color will still be black - You can have two class for each element, separated by one space. <p class="btn  btn-success"> </p>

Bundler allow you to specify exactly which third party software is required to run your program. Gemfile will list - all the dependencies/third party program required to run your program. - where to source those gems Gemfile.lock will list the exact version of the third party softwarre Gemfile.lock will be generated the first time you run 'bundle install'

* Sinatra is simply a Ruby Gem that is build specifically for easy web development. Its syntax is generally build around blocks like one below. get '/' do     @value = 'abc'     erb :layout end -sinatra route derived its name from HTTP method like GET, POST, or PUT. - here, '/' means a route for the web application like www.yourapp.com/ , it just specify the last character '/' for brevity. - any instance variable like @value will be accessible inside the templating language , in this case, erb file. - The last line 'erb :layout' will ask Sinatra to execute the template :layout * There are two important variable in Sinatra, namely params and session - session is instructing Sinatra to build a cookie that holds important information/build states that will last between multiple HTTP request, since HTTP is a stateless communication (ie. it forgets after each HTTP request). - You can push any information any information into session bec...

A method is simply a sequence of instruction that the computer will execute from start to finish. Eg: a = 10 def shout( a )     puts "hello!"     a = 15     puts a end shout(a) puts a # hello! # 15 # return nil # 10 - The method will take one or more input and output something after the sequence of instruction. - here, a is passed into the method shout , then assigned to a new variable 'a' and printed out as 15. - the original local var outside is still 10. - the method here has 3 lines of instruction. First one is output hello, second is assignment to number 15 to variable a , third one is output variable a. - The last line in the method's instruction will be returned . If we print what the value of the method's returned , it is nil puts shout(a) # nil