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FULL STACK JAVASCRIPT EXAM
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Javascript - Correct Answers -JavaScript is a multi-paradigm language, supporting imperative/procedural programming along with OOP (Object-Oriented Programming) and functional programming. JavaScript supports OOP with prototypal inheritance. Good to hear: Prototypal inheritance (also: prototypes, OLOO). Functional programming (also: closures, first-class functions, lambdas). Object-oriented programming (even: es6 classes, super, factories, getter/setter) Red flags: No clue what a paradigm is, no mention of prototypal oo, OOP or functional programming. What are two-way data binding and one-way data flow, and how are they different? - Correct Answers -Two-way data binding means that UI fields are bound to model data dynamically such that when a UI field changes, the model data changes with it and vice- versa. One way data flow means that the model is the single source of truth. Changes in the UI trigger messages that signal user intent to the model (or "store" in React). Only the model has access to change the app's state. The effect is that data always flows in a single direction, which makes it easier to understand. One way data flows are deterministic, whereas two-way binding can cause side-effects which are harder to follow and understand. What is functional programming? - Correct Answers -Functional programming produces programs by composing mathematical functions and avoids shared state & mutable data. Lisp (specified in 1958) was among the first languages to support functional programming and was heavily inspired by lambda calculus. Lisp and many Lisp family languages are still in everyday use today.
Functional programming is an essential concept in JavaScript (one of the two pillars of JavaScript). Several common useful utilities were added to JavaScript in ES5. What is Object Oriented Programming? - Correct Answers -Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects," which may contain data, in the form of fields, often known as attributes; and code, in the form of procedures, often known as methods. A feature of objects is that an object's procedures can access and often modify the data fields of the object with which they are associated (objects have a notion of "this" or "self"). In OOP, computer programs are designed by making them out of objects that interact with one another. There is a significant diversity of OOP languages, but the most popular ones are class-based, meaning that objects are instances of classes, which typically also determine their type. What does "favor object composition over class inheritance" mean? - Correct Answers - This is a quote from "Design Patterns: Elements of Reusable Object-Oriented Software". It means that code reuse should be achieved by assembling smaller units of functionality into new objects instead of inheriting from classes and creating object taxonomies. In other words, use can-do, has-a, or uses-a relationships instead of is-a relationships. Good to hear: Avoid class hierarchies. Avoid brittle base class problem. Avoid tight coupling. Avoid rigid taxonomy (forced is-a relationships that are eventually wrong for new use cases). Avoid the gorilla banana problem ("what you wanted was a banana, what you got was a gorilla holding the banana, and the entire jungle"). Make code more flexible. Red Flags: Fail to mention any of the problems above. Fail to articulate the difference between composition and class inheritance, or the advantages of composition. Node.js - Correct Answers -Node.js is a run-time JavaScript environment built on top of Chrome's V8 engine. It uses an event-driven, non-blocking I/O model. It is lightweight and so efficient. Node.js has a package ecosystem called npm. Node.js can be used to build different types of applications such as web application, real-time chat application, REST API server, etc. However, it is mainly used to build network programs like web servers, similar to PHP, Java, or ASP.NET. Node.js was developed by Ryan Dahl in 2009.
Asynchronous programming means that the engine runs in an event loop. When a blocking operation is needed, the request is started, and the code keeps running without blocking for the result. When the response is ready, an interrupt is fired, which causes an event handler to be run, where the control flow continues. In this way, a single program thread can handle many concurrent operations. User interfaces are asynchronous by nature, and spend most of their time waiting for user input to interrupt the event loop and trigger event handlers. Node is asynchronous by default, meaning that the server works in much the same way, waiting in a loop for a network request, and accepting more incoming requests while the first one is being handled. This is important in JavaScript, because it is a very natural fit for user interface code, and very beneficial to performance on the server. Good to hear: An understanding of what blocking means, and the performance implications. A knowledge of event handling, and why its essential for UI code. Red flags: Unfamiliar with the terms asynchronous or synchronous. Unable to articulate performance implications or the relationship between asynchronous code and UI code. Explain the difference between Relation DB vs. NoSQL - Correct Answers -RDBMS over NoSQL: Better for relational data that is structured and organized. Organize data through normalization Use Structured query language(SQL) which is easy to learn Maintains Data Integrity Data and its relationships are stored in separate tables ACID compliance, i.e., either all the transactions are committed or None Scale up/ Vertical Scaling NoSQL over RDBMS: Better for Unstructured and unpredictable Data Handles Big Data No predefined schema Cheaper to manage Scale-out/Horizontal Scaling BASE Transaction High performance, availability, and scalability
What are the different types of NoSQL databases? - Correct Answers -1. Key-value stores: The simplest, where every item in the database is stored as an attribute name (or "key") together with its value. Riak, Voldemort, and Redis are the most well-known in this category.
- Wide-column stores: It stores the data together as columns instead of rows and is optimized for queries over large datasets. The most popular are Cassandra and HBase.
- Document databases: It pairs each key with a complex data structure known as a document. Documents can contain many different key-value pairs, or key-array pairs, or even nested documents. MongoDB is the most popular of these databases.
- Graph databases: They are used to store information about networks, such as social connections. Examples are Neo4J and HyperGraphDB. What are different types of Web Services? - Correct Answers -1. SOAP Web Services: Runs on SOAP protocol and uses XML technology for sending data.
- Restful Web Services: It's an architectural style and runs on HTTP/HTTPS protocol almost all the time. REST is a stateless client-server architecture where web services are resources and can be identified by their URIs. Client applications can use HTTP GET/POST methods to invoke Restful web services. What are different HTTP Methods supported in Restful Web Services? - Correct Answers -Restful web services supported HTTP methods are — GET, POST, PUT, DELETE and HEAD. What is localStorage in HTML 5? - Correct Answers -It is a feature in HTML5 which let us store user data locally within the user's browser. How is localStorage different from Cookies? - Correct Answers -They are more secure because web pages can access only access data stored by itself. They are faster Easy to retrieve and write compare to cookies Not included with every server request Supports a significant amount of data and even won't affect performance. How is localStorage different from session storage? - Correct Answers -localStorage stores data with no expiration date whereas sessionStorage stores data for one session
