Added Interview Questions Folder

InterviewQuestions/EventBubbling.js

@@ -0,0 +1,31 @@
+// Event Bubbling and Capturing
+//when you have a nested elements in the dom and when you add a event to the last child it will follow pattern
+// as that child to till the parent
+// whereas in capturing the process is reverse
+
+// The process of propagating from nearest element to farthest element in the dom is called "EVENT BUBBLING"
+// The process of propagating from farthest element to nearest element in the dom is called "EVENT CAPTURING"
+// EVENT CAPTURING is also called as "TRICKLING"
+// stopPropagation() will stop the propagation either in event bubbling or in event capturing.
+
+
+const grandParent = document.getElementById('grand-parent');
+const parent = document.getElementById('parent');
+const child = document.getElementById('child');
+
+
+grandParent.addEventListener('click',() => {
+    console.log("Grand-Parent")
+},true)
+// The true argument refers to the event capturing and true says that implement capturing.
+
+parent.addEventListener('click',() => {
+    console.log("parent")
+},true)
+
+child.addEventListener('click',() => {
+    console.log("child")
+},true)
+
+// In the above example  in the case of false argument the event bubbling will occur and if you click on 
+//child div all the three log statements will appear because of the effect of event bubbling

README.md

@@ -5,3 +5,66 @@ This book will teach you the basics of programming and Javascript. Whether you a
 ![](./assets/intro.png)
 
 JavaScript (_JS for short_) is the programming language that enables web pages to respond to user interaction beyond the basic level. It was created in 1995, and is today one of the most famous and used programming languages.
+
+JavaScript was initially created to “make web pages alive”.
+
+The programs in this language are called scripts. They can be written right in a web page’s HTML and run automatically as the page loads.
+
+Scripts are provided and executed as plain text. They don’t need special preparation or compilation to run.
+
+In this aspect, JavaScript is very different from another language called Java.
+
+When JavaScript was created, it initially had another name: “LiveScript”. But Java was very popular at that time, so it was decided that positioning a new language as a “younger brother” of Java would help.
+
+But as it evolved, JavaScript became a fully independent language with its own specification called ECMAScript, and now it has no relation to Java at all.
+Today, JavaScript can execute not only in the browser, but also on the server, or actually on any device that has a special program called the JavaScript engine.
+
+The browser has an embedded engine sometimes called a “JavaScript virtual machine”.
+
+Different engines have different “codenames”. For example:
+
+ * V8 – in Chrome, Opera and Edge.
+* SpiderMonkey – in Firefox.
+* …There are other codenames like “Chakra” for IE, “JavaScriptCore”, “Nitro” and “SquirrelFish” for Safari, etc.
+The terms above are good to remember because they are used in developer articles on the internet. We’ll use them too. For instance, if “a feature X is supported by V8”, then it probably works in Chrome, Opera and Edge.
+
+How do engines work?
+Engines are complicated. But the basics are easy.
+
+The engine (embedded if it’s a browser) reads (“parses”) the script.
+Then it converts (“compiles”) the script to the machine language.
+And then the machine code runs, pretty fast.
+The engine applies optimizations at each step of the process. It even watches the compiled script as it runs, analyzes the data that flows through it, and further optimizes the machine code based on that knowledge.
+
+What can in-browser JavaScript do?
+Modern JavaScript is a “safe” programming language. It does not provide low-level access to memory or CPU, because it was initially created for browsers which do not require it.
+
+JavaScript’s capabilities greatly depend on the environment it’s running in. For instance, Node.js supports functions that allow JavaScript to read/write arbitrary files, perform network requests, etc.
+
+In-browser JavaScript can do everything related to webpage manipulation, interaction with the user, and the webserver.
+
+For instance, in-browser JavaScript is able to:
+
+Add new HTML to the page, change the existing content, modify styles.
+React to user actions, run on mouse clicks, pointer movements, key presses.
+Send requests over the network to remote servers, download and upload files (so-called AJAX and COMET technologies).
+Get and set cookies, ask questions to the visitor, show messages.
+Remember the data on the client-side (“local storage”).
+What CAN’T in-browser JavaScript do?
+JavaScript’s abilities in the browser are limited for the sake of a user’s safety. The aim is to prevent an evil webpage from accessing private information or harming the user’s data.
+
+Examples of such restrictions include:
+
+JavaScript on a webpage may not read/write arbitrary files on the hard disk, copy them or execute programs. It has no direct access to OS functions.
+
+Modern browsers allow it to work with files, but the access is limited and only provided if the user does certain actions, like “dropping” a file into a browser window or selecting it via an <input> tag.
+
+There are ways to interact with camera/microphone and other devices, but they require a user’s explicit permission. So a JavaScript-enabled page may not sneakily enable a web-camera, observe the surroundings and send the information to the NSA.
+
+Different tabs/windows generally do not know about each other. Sometimes they do, for example when one window uses JavaScript to open the other one. But even in this case, JavaScript from one page may not access the other if they come from different sites (from a different domain, protocol or port).
+
+This is called the “Same Origin Policy”. To work around that, both pages must agree for data exchange and contain a special JavaScript code that handles it. We’ll cover that in the tutorial.
+
+This limitation is, again, for the user’s safety. A page from http://anysite.com which a user has opened must not be able to access another browser tab with the URL http://gmail.com and steal information from there.
+
+JavaScript can easily communicate over the net to the server where the current page came from. But its ability to receive data from other sites/domains is crippled. Though possible, it requires explicit agreement (expressed in HTTP headers) from the remote side. Once again, that’s a safety limitation.