what is Emmet?
Emmet is something that makes our code write faster as compared to the normal writing style it is a kind of shortcut that you use to increase your productivity here are some shortcuts to give you glims of how the thing works with the help of emmet.
If you Write ${This is Heading$}*6
So this will create 6 heading like this:
<h1>This is Heading</h1>
<h2>This is Heading</h2>
<h3>This is Heading</h3>
<h4>This is Heading</h4>
<h5>This is Heading</h5>
<h6>This is Heading</h6>
There are so many ways that enhanced your writing speed here is a cheatsheet link you can go through it
Difference between library and framework
Library
So let's assume the library is your own room means you can arrange things in a way that you like in this way in the library you are the one who writes code and use that chunk of code where you want nobody everything that is written done by you only there are many libraries like J query , React.js , underScore.js and manymore.
FrameWork
The framework is something like your classroom you can not do the thing which you like so the framework is something that builds by many libraries with the help of the framework we create an application
In the library, we are calling the function but in a framework, the framework is the one that takes care of that function call we are taking an example of bootstrap so if you want to use bootstrap so need to include cdn link so that CDN link is the one who called the bootstrap components there are many frameworks like bootstrap, Angular.js and many more.
What is CDN now?
CDN Stands for content delivery network whenever we click on the site that we want so it takes some requests and delivers you a wanted side for that example your website server is located in another country in that case website loading will be slow and ruin the user experience so CDN comes in a picture, in that case, it created a local file into the nearest database of that country and every time someone request for the site it will deliver quickly from there it works as a content delivery network.
Why is react known as react?
React is called React because it has the ability to react to changes in data .whenever data which is in a react component changes it will automatically re-render that component so that it will reflect the new data.
React and ReactDom
In order to work in React you have to include react and react-dom so there is react something that creates the element or you can say create a view and react-dom is responsible to render that created element into your webpage.
Async and defer in js
when you use async in your script tag it loaded the script along with the Html and the script does not block HTML loading/parsing but in the execution time, it blocks the HTML parsing. In a similar way defer load the script but only executed after HTML execution.