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AJAX Angular CSS CSS3 HTML HTML5 JavaScript jQuery NodeJS UI

UI Architect Interview Questions and Answers

what is tail call optimization ?
TCO (Tail Call Optimization) is the process by which a smart compiler can make a call to a function and take no additional stack space.

Recursive function approach has a problem. It builds up a call stack of size O(n), which makes our total memory cost O(n). This makes it vulnerable to a stack overflow error, where the call stack gets too big and runs out of space. Tail Cost Optimization (TCO) Scheme. Where it can optimize recursive functions to avoid building up a tall call stack and hence saves the memory cost.

what is Map, Set, WeakMap and WeakSet ?
Map is a collection of keyed data items, just like an Object. But the main difference is that Map allows keys of any type.

A Set is a collection of values, where each value may occur only once means it will contain unique set of keys. 

WeakSet is a special kind of Set that does not prevent JavaScript from removing its items from memory. WeakMap is the same thing for Map.
WeakMap does not support iteration and methods keys(), values(), entries(), so there’s no way to get all keys or values from it.

Map – is a collection of keyed values.

The differences from a regular Object:

Any keys, objects can be keys.
Iterates in the insertion order.
Additional convenient methods, the size property.
Set – is a collection of unique values.

Unlike an array, does not allow to reorder elements.
Keeps the insertion order.
Collections that allow garbage-collection:

WeakMap – a variant of Map that allows only objects as keys and removes them once they become inaccessible by other means.

It does not support operations on the structure as a whole: no size, no clear(), no iterations.
WeakSet – is a variant of Set that only stores objects and removes them once they become inaccessible by other means.

Also does not support size/clear() and iterations.
WeakMap and WeakSet are used as “secondary” data structures in addition to the “main” object storage. Once the object is removed from the main storage, if it is only found in the WeakMap/WeakSet, it will be cleaned up automatically.

how to do peer to peer communication in ANgular ?

what is directive & components in angular ?

if loop functions are removed from script, how can you achieve same functionality ?

how to drop both data and collection in mongodb ?

what is generic types in Typescript ? advantages ?

how to define custom types in Typescript ?

how to capture the process specific exceptions in NodeJS ?

how do you print name of file currently executing in NodeJS ?

how to use custom pipes in Angular ? can you pass additional parameters in custom pipes ?

what is the max data can be stored in a mongodb document ?

how to acheieve variable length documents in mongodb ?

how do you set autoincrement field in mongodb ?

what is the difference between throttling & debouncing ?
Throttling enforces a maximum number of times a function can be called over time. As in “execute this function at most once every 100 milliseconds.”
Debouncing enforces that a function not be called again until a certain amount of time has passed without it being called. As in “execute this function only if 100 milliseconds have passed without it being called.”

what is event bubbling ? how to stop ?
what is digest cycle in angularJS ?
how to stop propgation ?
what is interpolation ? how does it work ?
what is shadow dom ?
what is webworker ?
how to cache the page/data in HTML 5 ?
how to give offline view expereince in HTML5 ?
what is lazyloadng? how it works ?
what are pure / impure pipes ?
what is redux ? how does it work ?
unit testing code coverage how to check ?
what tool used for unit test ?
streaming , how does it work ?
any custom video/audio player developed?
how does cache works in HTML5 ?
what is method chaining ?
difference between canvas vs SVG ?
what is XSS and how to avoid it ?

difference between Responsive and Adaptive design ?
diff b/w flexbar & grid designs ?
what is cors ? how to allow ?
symmetric & asymetric keys ?
scope usage in OAuth token ?
explain component lifecycle
how to use service in Angular ?
what is event emitters ?
latest ECMA version ?
INPUT & OUTPUT variables usage in Angular
explain Digest Lifecycle in Angular ?
difference between Angular 1.x & Angular 2.x
what is SASS & SCSS ?
what is ViewChild ? OR ViewCildren ?

Explain the following :

Directives,
decorators,
Services,
Modules,
Data Binding,
Components,
Filters,
DOM ,
Events ,
Routing,
Dependency injection.

Categories
Agile AJAX Angular CSS CSS3 HTML HTML5 JavaScript jQuery NodeJS UI

Javascript / UI / Angular Architect Questions and Answers

1.Difference between var let and const. ?

a. Var is hoisted in JS, let and const are not hoisted.

b. Let, const are block level, var is function level The candidate has to tell at least one of these apart from any other difference he tells.

2. What is a closure and how does it work

a. A closure is an inner function that has access to the outer (enclosing) function’s variables—scope chain.

A closure is an inner function that has access to the outer (enclosing) function’s variables—scope chain.

3. What is a JavaScript class

a. ES 6 standard introduced classes in JS, which internally use the prototypal approach to implement Class .

4. How does JS implement inheritance

a. JS uses prototypal inheritance in which objects inherit properties from other objects (or) JS uses prototypes to implement inheritance

5. What is the difference between == and === in JS

a. == checks only for the value, where === checks for both value and data type

6. What is the use of hasOwnProperty method in JS

a. This method returns true, only when the passed property is present directly on the object.

7. Explain call, apply and bind

a. Call and apply are used to invoke a method, by setting the context of ‘this’ keyword. Call takes comma separated individual parameters, and apply takes array of parameters as arguments

b. Bind method does the same operation as call and apply, but returns a new function definition instead of invoking the method

8. What is ‘arguments’ keyword in JS

a. Arguments is a special property in every function, that holds all the parameters passed to that function. Its an array-like object.

9. What is arrow function

a. Arrow function is introduced in ES 6 standard of JS, and does implicit binding of this property.

10. What are benefits of TypeScript

a. * TS provides type safety for the variables

Skills checked:

JS core – Intermediate / Advanced

  1. What is a closure and how it works in JavaScript
  2. What is a ‘hosting’ , How this works in JavaScript ?
  3. call, apply and bind with example
  4. Event bubbling and Event capturing
  5. event delegation
  6. prototypical inheritance / prototypical chain
  7. strict mode and usual mode
  8. What is EventLoop?

ECMA

  1. Difference between var, let and const?
  2. What is a promise and how it works?
  3. What is a arrow function and its difference from function syntax?
  4. Generator and how it works
  5. JS modules, export and export default
  6. async/await

Angular – Intermediate / Advanced

  1. Virtual DOM concept.
  2. Subscribe, Observables and Promises.
  3. Different ways of data bindings.
  4. Sequence of Angular Lifecycle Hooks
  5. Routing
  6. Reactive Forms.

React JS and Redux – Novice / Intermediate

  1. Virtual DOM concept.
  2. Explain lifecycle of React component.
  3. Difference between state and props.
  4. Redux
  5. Role of reducer

HTML – Novice / Intermediate

  1. What is a Doctype?
  2. quirks mode and standart mode
  3. new features in html5
  4. Html storage Localstorage and sessionstorage

CSS – Novice

  1. Difference between adaptive and responsive design?
  2. What is a repaint and reflow?
  3. Media query.
  4. Layout Methodology.
  5. How browser search selector?

Networking – Intermediate

  1. What is REST?
  2. REST principles.
  3. Difference between POST and PUT requests

Design Patterns – Advanced

  1. Factory Patterns
  2. Singleton Patterns

Unit testing

  1. TDD/BDD
  2. jasmine/karma

Processes

  1. GIT
  2. Code review process and tools
  3. CI/CD
  4. SOLID
  5. SCRUM
  6. Webpack
  7. IDE

Categories
Angular JavaScript NodeJS UI

BARCO – MEAN Architect – NodeJS developer Interview Questions and Answer

BARCO – MEAN Architect – NodeJS developer Interview Questions and Answer

what is tail call optimization ?
TCO (Tail Call Optimization) is the process by which a smart compiler can make a call to a function and take no additional stack space.

Recursive function approach has a problem. It builds up a call stack of size O(n), which makes our total memory cost O(n). This makes it vulnerable to a stack overflow error, where the call stack gets too big and runs out of space. Tail Cost Optimization (TCO) Scheme. Where it can optimize recursive functions to avoid building up a tall call stack and hence saves the memory cost.

what is Map, Set, WeakMap and WeakSet ?
Map is a collection of keyed data items, just like an Object. But the main difference is that Map allows keys of any type.

A Set is a collection of values, where each value may occur only once means it will contain unique set of keys. 

WeakSet is a special kind of Set that does not prevent JavaScript from removing its items from memory. WeakMap is the same thing for Map.
WeakMap does not support iteration and methods keys(), values(), entries(), so there’s no way to get all keys or values from it.

Map – is a collection of keyed values.

The differences from a regular Object:

Any keys, objects can be keys.
Iterates in the insertion order.
Additional convenient methods, the size property.
Set – is a collection of unique values.

Unlike an array, does not allow to reorder elements.
Keeps the insertion order.
Collections that allow garbage-collection:

WeakMap – a variant of Map that allows only objects as keys and removes them once they become inaccessible by other means.

It does not support operations on the structure as a whole: no size, no clear(), no iterations.
WeakSet – is a variant of Set that only stores objects and removes them once they become inaccessible by other means.

Also does not support size/clear() and iterations.
WeakMap and WeakSet are used as “secondary” data structures in addition to the “main” object storage. Once the object is removed from the main storage, if it is only found in the WeakMap/WeakSet, it will be cleaned up automatically.

how to do peer to peer communication in ANgular ?

what is directive & components in angular ?

if loop functions are removed from script, how can you achieve same functionality ?

how to drop both data and collection in mongodb ?

what is generic types in Typescript ? advantages ?

how to define custom types in Typescript ?

how to capture the process specific exceptions in NodeJS ?

how do you print name of file currently executing in NodeJS ?

how to use custom pipes in Angular ? can you pass additional parameters in custom pipes ?

what is the max data can be stored in a mongodb document ?

how to achieve variable length documents in mongodb ?

how do you set auto increment field in mongodb ?

Categories
AJAX Angular CSS CSS3 HTML HTML5 JavaScript jQuery NodeJS UI Uncategorized VueJS

SAP – UI Architect – Angular Interview Questions and Answers

List and explain XSS attack types?

Cross-site scripting (XSS) is a code injection attack that allows an attacker to execute malicious JavaScript in another user’s browser.

XSS attacks are of three types:

  • Persistent XSS, where the malicious string originates from the website’s database.
  • Reflected XSS, where the malicious string originates from the victim’s request.
  • DOM-based XSS, where the vulnerability is in the client-side code rather than the server-side code.

Methods of preventing XSS

  • Encoding, which escapes the user input so that the browser interprets it only as data, not as code.
  • Validation, which filters the user input so that the browser interprets it as code without malicious commands.

What is CORS , how to manage? How to secure the requests?

Cross-Origin Resource Sharing (CORS) is a mechanism that uses additional HTTP headers to tell a browser to let a web application running at one origin (domain) have permission to access selected resources from a server at a different origin. A web application makes a cross-origin HTTP request when it requests a resource that has a different origin (domain, protocol, and port) than its own origin.

two response headers are most important for security:  

  • Access-Control-Allow-Origin specifies which domains can access a site’s resources. For example, if ABC Corp. has domains ABC.com and XYZ.com, then its developers can use this header to securely grant XYZ.com access to ABC.com’s resources. 
  • Access-Control-Allow-Methods specifies which HTTP request methods (GET, PUT, DELETE, etc.) can be used to access resources. This header lets developers further enhance security by specifying what methods are valid when XYZ accesses ABC’s resources. 

As CORS can lead to multiple security vulnerabilities , so instead of allowing CORS use a trusted server as a proxy / reverse proxy and allow all requests/resources to be served  from that dedicated server.

What is Virtual polymorphism ?

Polymorphism is the ability for objects of different classes related by inheritance to respond differently to the same member function call.

virtual function allows a programmer to call a function and let the program determine dynamically which version of the function to use.
To enable this type of behavior, the function will be declared in the base class as a virtual function and then be redefined in each of the derived classes.
To declare a virtual function, precede the function’s prototype with the keyword virtual in the base class.
Combination of both Virtual Function with polymorphism concept is called Virtual Polymorphism.

Write a Sql query for products table to get total price of products sold in a quarter ?

 SELECT
  productname, 
  SUM(price) as total_count
  FROM products
  WHERE `date` >= startdate AND `date` <= enddate
  GROUP BY productname
  ;

Write a Sql query for products table to get total price of products sold in a quarter ?

To calculate any factorial in real-time, you can speed it with a cache, saving the numbers you’ve calculated before.

factorial = (function() {
    var cache = {},
        fn = function(n) {
            if (n === 0) {
                return 1;
            } else if (cache[n]) {
                return cache[n];
            }
            return cache[n] = n * fn(n -1);
        };
    return fn;
})();

Types of requests which can be handled through browser?

HTTP, HTTPS, FILE, and FTP protocols are supported by most of the commonly used browsers.

What is promise? Advantages of it ?

A Promise is an object representing the eventual completion or failure of an asynchronous operation. Essentially, a promise is a returned object to which you attach callbacks, instead of passing callbacks into a function.

Advantages of promises are

  • Callbacks will never be called before the completion of the current run of the JavaScript event loop.
  • Callbacks added with then() even after the success or failure of the asynchronous operation, will be called, as above.
  • Multiple callbacks may be added by calling then() several times. Each callback is executed one after another, in the order in which they were inserted.
  • One of the great things about using promises is chaining.

How to improve the Performance of webpage?

  • Reduce External HTTP Requests
  • Minify CSS, JS and HTML
  • Compress Components with Gzip
  • Optimize Your Images
  • Add CSS at top/header section
  • Add JS at bottom section
  • Reduce DNS Lookups
  • Use CDN and Cache
  • Make Fewer HTTP Requests
  • Avoid empty src or href
  • Add Expires Headers
  • Avoid CSS Expressions
  • Avoid URL Redirects
  • Remove Duplicate JavaScript and CSS
  • CleanUP the unecessary code
  • Configure Entity Tags (ETags)
  • Reduce the Number of DOM Elements
  • Avoid HTTP 404 (Not Found) Error
  • Do Not Scale Images in HTML
  • Make favicon Small and Cacheable

IF Request/Response taking too much time than How to keep alive the request ?

A Request/Gateway Timeout response code indicates that the server did not receive a complete request from the client within a specific period of time tracked by the server.
You can set custom timeout for your http request in the second parameter of http.get() method:
$http.get(‘request-path’, {timeout: 300000});
This will set timeout to 300 seconds = 5 minutes. Increasing it to something much larger should help.
OR
req.setTimeout(0) for no timeout for all requests
Another solution is doing a long polling or short polling to keep alive the request.

DB 2 queries same record update? How to manage? How to intimate the second request to update itself?

Use SQL transaction statements like BEGIN and COMMIT to avoid concurrent updates to same record.
OR
You may have additional field which indicates that column is being edited. When first user starts work, the field would be updated. The second user would query object with ‘on hold’ status and your code would handle this.

Lot of requests , how to manage?

  • Use CDN for optimized content delivery
  • Use Cache Layers like memcache , redis etc..
  • Use Load Balancing techniques for Application Servers / Cache Layers
  • Use Master / Salve configuration for DB Servers

Same application, for 2 different companies but for all users, request to come, how to manage?

Use Proxy / Reverse proxy configuration along with a flag specific to company to manage the requests to handle internally from different servers.

Bind, apply and call difference in angular ?

The bind() method creates a new function that, when called, has its “this” keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.
fun.bind(thisarg[, arg1[,arg2[,….]]])

Function.call allows us to set the this value of a function manually. Instead of simply calling a function like fn(), we use fn.call(param), passing in the object we want this to equal as the parameter.
call also allows us to pass in parameters to the function being called. Anything given after the object to be bound to thiswill be passed along to the function.

Function.apply works the same exact way as call, except instead of passing in arguments one by one, we pass in an array of arguments that gets spread into the function.

In call method parameter will be passed separately. whereas in apply you can pass parameters as Array arguments.

Globalization or internationalization , how to do in angular?

Internationalization (i18n) is the process of developing products in such a way that they can be localized for languages and cultures easily. Localization (l10n), is the process of adapting applications and text to enable their usability in a particular cultural or linguistic market.
internationalizing an application means abstracting all of the strings and other locale-specific bits (such as date or currency formats) out of the application. Localizing an application means providing translations and localized formats for the abstracted bits.
AngularJS supports i18n/l10n for date, number and currency filters.
Localizable pluralization is supported via the ngPluralize directive.
All localizable AngularJS components depend on locale-specific rule sets managed by the $locale service.

How to avoid same button multiple clicks  ?

There are multiple ways to avoid multiple clicks of a same button

  • Once the click event is fired , disable the button till event response is processed
  • Unbind the click event on first click event
  • Provide a time interval for between the same object click event
Categories
JavaScript PHP

How to run production mode in vue.js with laravel ?

How to run production mode in vue.js with laravel  ?   

Method 1 :

In Laravel , Vue.js is included through NPM package and will be compiled as part of webpack in node stack. so while executing the npm assets compile command we need to mention it to compile in production mode. here is the command. 
npm run production  
Method 2 : 
In Laravel, Add an environment variable in laravel configuration and based on the load the Vue Configurations in the run time.

Environment Variable Creation Guide refer : https://laravel.com/docs/5.6/mix#environment-variables

Define :
MIX_ENV_MODE=production

Usage:

process.env.MIX_ENV_MODE
In any of the scripts file make sure to add conditional execution of vue.js configurations as below :
if (process.env.MIX_ENV_MODE === 'production') {
    Vue.config.devtools = false;
    Vue.config.debug = false;
    Vue.config.silent = true; 
}