Member of Technical Staff

The Critical Rendering Path is the sequence of steps the browser goes through to convert the HTML, CSS, and JavaScript into pixels on the screen.
Web performance includes the server requests and responses, loading, scripting, rendering, layout, and the painting of the pixels to the screen.
A request for a web page or app starts with an HTML request. The server returns the HTML - response headers and data. The browser then begins parsing the HTML, converting the received bytes to the DOM tree. The browser initiates requests every time it finds links to external resources, be they stylesheets, scripts, or embedded image references. Some requests are blocking, which means the parsing of the rest of the HTML is halted until the imported asset is handled. The browser continues to parse the HTML making requests and building the DOM, until it gets to the end, at which point it constructs the CSS object model. With the DOM and CSSOM complete, the browser builds the render tree, computing the styles for all the visible content. After the render tree is complete, layout occurs, defining the location and size of all the render tree elements. Once complete, the page is rendered, or 'painted' on the screen.

Asynchronous JavaScript: Asynchronous code allows the program to be executed immediately where the synchronous code will block further execution of the remaining code until it finishes the current one. This may not look like a big problem but when you see it in a bigger picture you realize that it may lead to delaying the User Interface.

Classes are bits of code that encompass multiple objects, methods and allow manipulation for its member variables and functions. Within each language, a class has different syntax and the same holds true for Javascript. Using the class functionality one can define the constructor and the prototype functions for the member objects in one encompassing block.
To create a class : 
1. A class is created using the keyword class : 
class Student{
// Elements within the class are declared and defined inside the brackets
}
2. A class has a default constructor which is empty but can also be defined within the class method.

Mobile-first design is an approach in which web designers start product design for mobile devices first. This can be done by sketching or prototyping the web-app’s design for the smallest screen first and gradually working up to larger screen sizes. Prioritizing design for mobiles makes sense as there are space limitations in devices with smaller screen sizes and teams need to ensure that the key elements of the website are prominently displayed for anyone using those screens.