[js, common, html] questions update

Author: wwwebman

readme.md

@@ -1,37 +1,43 @@
 ![github front end develeper interview questions and answers teaser](https://webman.pro/assets/img/main/webman-front-end-interview-questions-answers-github.jpg)
 
 # Front End Interview Questions and Answers
-This information is intended for the potential Front End Developer candidates.
-The following list includes a basic theoretical and code questions.
+This information is intended for the potential Front End Developer candidates. The following list includes a basic theoretical and code questions.  
+I hope, that my experience and experience of other developers will helps you to get the best interview results.    
 
-I hope, that my experience and experience of other developers will helps you to get the best interview results.
+**P.S. My main goal is to help candidates and to myself to get more web knowledge. Based on this point, let's improve the hard skills of Front-End community together. Please,  send you Front-End interview questions via pull request.**
 
 ## List of Content
 1. [Common interview questions](#common-interview-questions)
 1. [Common technical interview questions](#common-technical-interview-questions)
 1. [HTML](#html-interview-questions)
 1. [CSS](#css-interview-questions)
 1. [Javascript](#javascript-interview-questions)
+    * [Junior candidate](#junior-candidate)
+    * [Middle candidate](#middle-candidate)
+    * [Senior candidate](#senior-candidate)
 1. [Javascript Coding](#javascript-coding-questions)
 1. [React interview questions](#react-interview-questions)
 1. [Funny Questions](#funny-questions)
 1. [Contributing](#contributing)
-    1. [Examples for Answers classification](#answers-classification)
+    * [Answers classification](#answers-classification)
 
 ## Common interview questions
 1. What was the most interesting solution did you implemented at the last project? 
 1. What is the last book you read?
 1. How big your team ever was?
 1. Have you ever worked in [Agile, Scrum or Kanban](https://www.smartsheet.com/agile-vs-scrum-vs-waterfall-vs-kanban) environments?
-1. What developers of Front End community do you know?
-1. What is 'Gangs of four'?
+1. Which developers of Front End community do you know?
+1. What do you hear about 'Gangs of four'?
+1. Explain the difference between unit tests and integration tests? - [@answer--stackoverflow](https://stackoverflow.com/a/5357837/5513804)
+1. What are the most common types of web attacks do you know? - [@answer--blog.sucuri.net](https://blog.sucuri.net/2014/11/most-common-attacks-affecting-todays-websites.html)
+1. What is 'duck typing'? - [@answer--wikipedia](https://en.wikipedia.org/wiki/Duck_typing)
 
 ## Common technical interview questions
 1. What is [REST](http://www.restapitutorial.com/)? - [@library--restcookbook](http://restcookbook.com/)
 1. What is the difference between PUT and PATCH methods in REST? - [@answer--stackoverflow](https://stackoverflow.com/questions/21660791/what-is-the-main-difference-between-patch-and-put-request)
 1. Tell about the differences between [websockets](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket), long polling and [SSE](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events). - [@answer--stackoverflow](https://stackoverflow.com/questions/11077857/what-are-long-polling-websockets-server-sent-events-sse-and-comet)
 1. What is CORS? - [@answer--maxcdn.com](https://www.maxcdn.com/one/visual-glossary/cors/), [@doc--mdn](https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS)
-1. What is the main things you can do to increase page speed loading? - [@answer--crazyegg.com](https://www.crazyegg.com/blog/speed-up-your-website/)
+1. List the main things you can do to increase page speed loading? - [@answer--crazyegg.com](https://www.crazyegg.com/blog/speed-up-your-website/)
 1. Progressive enhancement vs graceful degradation. What is the difference? - [@answer--w3](https://www.w3.org/wiki/Graceful_degradation_versus_progressive_enhancement)
 1. Do you use [Grunt](https://gruntjs.com/), [Gulp](https://gulpjs.com/), [Webpack](https://webpack.github.io/) or Browserify in your projects?
 1. What do you know about "60fps"? What way to achieve this? - [@answer--github](https://github.com/vasanthk/browser-rendering-optimization)
@@ -41,6 +47,7 @@ I hope, that my experience and experience of other developers will helps you to
 1. Could you list main HTML5 tags? - [@doc--mdn](https://developer.mozilla.org/en-US/docs/Web/HTML/Element)
 1. What does mean optional closing tag? - [@doc--w3](https://www.w3.org/TR/REC-html40/index/elements.html) 
 1. When and how to preload resources? - [@answer--medium](https://medium.com/reloading/preload-prefetch-and-priorities-in-chrome-776165961bbf)
+1. What is different between id and class?
 
 ## CSS Interview Questions
 1. What is different between mobile first and desktop first - [@answer--codemyviews.com](https://codemyviews.com/blog/mobilefirst )?
@@ -49,13 +56,27 @@ I hope, that my experience and experience of other developers will helps you to
 1. What preprocessor do you use ([Sass](http://sass-lang.com/), [Less](http://lesscss.org/))?
 
 ## Javascript Interview Questions
-1. Who is the author of JavaScript Language? - 
+
+#### Junior candidate
+1. Who is the author of JavaScript Language?
+1. What is the best book for learning JavaScript? Why? - [@answer-good-js-books--github](https://github.com/wwwebman/js-books-backpack)
+1. What type of NaN? How to check if a value is NaN?
+1. What the reason that `window.window === window` return true? - [@doc--mdn](https://developer.mozilla.org/pl/docs/Web/API/Window/window)
+1. What is the outcome of Javascript calculation? `1/0 = ?`
+
+#### Middle candidate
+1. What does `this` refer to? - [@answer--javascriptissexy](http://javascriptissexy.com/understand-javascripts-this-with-clarity-and-master-it/)
 1. What is the JavaScript Event Loop? - [@answer--altitudelabs.com](http://altitudelabs.com/blog/what-is-the-javascript-event-loop/), [@video-Roberts--youtube](https://www.youtube.com/watch?v=8aGhZQkoFbQ&t=1244s)
 1. What is the Event Delegation? - [@answer--davidwalsh](https://davidwalsh.name/event-delegate), [@code-example](https://jsfiddle.net/thisman/h2eqfsx6/)
 1. What is the difference between e.target and e.currentTarget? - [@doc--mdn](https://developer.mozilla.org/en-US/docs/Web/API/Event/currentTarget), [@code-example](https://jsfiddle.net/thisman/gkdeocd6/)
-1. What patterns do you know and successfully use in JavaScript?
 1. What is [`Window.postMessage()`](https://davidwalsh.name/window-postmessage) and where it can be used? - [@doc--mdn](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage)
 1. Is there any difference between Promises and callbacks? Which is better? - [@answer-callback--callbackhell.com](http://callbackhell.com/),  
+1. What is the recursion? When using of the recursion can be useful in Javascript? - [@answer--medium](https://medium.com/@dis_is_patrick/practical-uses-for-recursive-javascript-b8f142552f8b)
+
+#### Senior candidate
+1. What patterns do you know and successfully use in JavaScript?
+1. What is the different between Deferred and Promise objects? Where is Deferred object used?
+1. What is the problem throttling and debouncing are resolved? What is the core difference between them? - [@answer--medium](https://medium.com/@_jh3y/throttling-and-debouncing-in-javascript-b01cad5c8edf)
 
 ## Javascript Coding Questions
 * Write a `pipefy` function where a string received is returned, but with the `|` character between each character. Make it possible to execute function in this way: `'javascript'.pipefy()`. - [@code-answer](https://jsfiddle.net/thisman/6ynaf3ot/)
@@ -65,7 +86,7 @@ I hope, that my experience and experience of other developers will helps you to
 // Code below must return true
 alert(factorial(3) === 6 && factorial(0) === 1);
 ```
-* Which line of the below code will be executed  cowith an error. Why?
+* Which line of the below code will be executed with an error. Why?
 ```js
 10 .toString();
 (10).toString();