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Top 100+ Koa.js Interview Questions And Answers - May 31, 2020

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Top 100+ Koa.js Interview Questions And Answers

Question 1. What Is Koa?

Answer :

Koa provides a minimal interface to us to build our applications. It is a very small framework(six hundred LoC) which presents us the required equipment to construct our app and is pretty flexible, there are various modules to be had on npm for Koa, which can be immediately plugged into it. Koa may be idea of because the center of specific.Js without all the bells and whistles.

Question 2. Why Koa?

Answer :

Koa has a small footprint(600 LoC) and is a very thin layer of abstraction over node to create server facet apps. It is completely pluggable and has a massive network. This also permits us to effortlessly extend koa and use it in keeping with our wishes. It is built using the bleeging facet generation(ES6) which offers it an aspect over older frameworks like explicit.

Angular JS Interview Questions
Question three. What Is Pug?

Answer :

Pug(earlier known as Jade) is a terse language for writing HTML templates. It:

Produces HTML
Supports dynamic code
Supports reusability (DRY)
It is one of the most popular templating language used with koa.
Question 4. What Is Mongodb And Mongoose?

Answer :

MongoDB is an open-source, record database designed for ease of development and scaling. We'll use this database to save information.

Mongoose is a client API for node.Js which makes it easy to get admission to our database from our koa software.

Ext JS Tutorial
Question 5. Explain Koa.Js Environment?

Answer :

To get commenced with growing the use of the Koa framework, you want to have Node and npm(node package manager) hooked up. If you don’t already have these, head over to Node setup to put in node to your neighborhood machine. Confirm that node and npm are installed by means of jogging the subsequent commands to your terminal.

$ node --version
$ npm --model

You have to get an output much like:

v5.Zero.0
3.Five.2

Please ensure your node version is above 6.Five.Zero.

Now that we've Node and npm set up, allow us to understand what npm is and the way to use it.

Ext JS Interview Questions
Question 6. What Is Node Package Manager(npm)?

Answer :

npm is the package deal supervisor for node. The npm Registry is a public series of applications of open-source code for Node.Js, the front-quit internet apps, cell apps, robots, routers, and countless different wishes of the JavaScript network. Npm permits us to get entry to these kinds of packages and set up them domestically. You can browse through the listing of packages to be had on npm at npmJS.

Question 7. How To Use Npm?

Answer :

There are 2 methods to install a package deal using npm: globally and regionally.

Globally: This technique is usually used to put in development tools and CLI primarily based applications. To deploy a package globally, use:
$ npm installation -g <package-name>
Locally: This approach is normally used to put in frameworks and libraries. A locally set up package can be used only in the directory it is established. To deploy a package deal domestically use the equal command as above without the -g flag.
$ npm install <package-name>
Whenever we create a venture the use of npm, we want to offer a package deal.Json file, which has all of the information about our assignment. Npm make it smooth for us to set up this document. Let us set up our development project.

Fire up your terminal/cmd, create a new folder named hi there-international and cd into it: npm into it
Now to create the package deal.Json report using npm, use the subsequent.--npm init
Now we've our package.Json record set up, we’ll set up koa. To set up koa and add it in our bundle.Json file, we use the subsequent command:
$ npm deploy --store koa

To affirm koa set up efficaciously, run

$ ls node_modules #(dir node_modules for windows)
Node.Js Tutorial Node.Js Interview Questions
Question 8. What Is Koa.Js Generators?

Answer :

One of the maximum exciting new capabilities coming in JavaScript ES6 is a new breed of feature, called a generator. Before turbines, the entire script used to normally execute in a pinnacle to backside order, without an clean way to stop code execution and resuming with the identical stack later. Generators are capabilities which can be exited and later re-entered. Their context (variable bindings) will be saved across re-entrances.

Generators allow us to stop code execution in among. So we could have a look at a simple generator:

var generator_func = feature* ()
yield 1;
yield 2;
;
var itr = generator_func();
console.Log(itr.Next());
console.Log(itr.Subsequent());
console.Log(itr.Next());

Question 9. What Is Koa.Js Routing?

Answer :

Web frameworks provide sources inclusive of HTML pages, scripts, images, and so on. At extraordinary routes. Koa does not support routes in the core module. We want to apply the koa-router module to easily create routes in koa. Install this module using:

npm install --shop koa-router

Now that we have koa-router mounted, shall we have a look at a easy GET direction instance:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var _ = router(); //Instantiate the router
_.Get('/howdy', getMessage); // Define routes
characteristic *getMessage()
this.Body = "Hello world!";
;
app.Use(_.Routes()); //Use the routes defined the use of the router
app.Listen(3000);

If we run our software and go to localhost:3000/whats up, the server gets a get request at path "/hello", our koa app executes the callback characteristic connected to this path and sends "Hello World!" as the response.

ReactJS Interview Questions
Question 10. What Is Koa.Js Url Building?

Answer :

We can now define routes, however those are static or constant. To use dynamic routes, we want to offer specific types of routes. Using dynamic routes lets in us to skip parameters and process based on them. Here is an example of a dynamic course:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var _ = router();
_.Get('/:id', sendID);
characteristic *sendID()
    this.Frame = 'The identity you unique is ' + this.Params.Identity;

app.Use(_.Routes());
app.Concentrate(3000);

JasmineJS Tutorial
Question 11. What Is Pattern Matched Routes?

Answer :

You also can use regex to limit URL parameter matching. Let's say you need the identification to be five digits lengthy variety. You can use the subsequent path definition:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var _ = router();
_.Get('/things/:identification([0-9]five)', sendID);
feature *sendID()
this.Frame = 'identity: ' + this.Params.Id;

app.Use(_.Routes());
app.Pay attention(3000);

Note that this may only fit the requests which have a five digit long identification. You can use more complicated regexes to healthy/validate your routes. If none of your routes suit the request, you'll get a Not discovered message as reaction.

Backbone.Js Interview Questions
Question 12. What Is Koa.Js Http Methods?

Answer :

The HTTP method is furnished within the request and specifies the operation that the purchaser has asked. The underneath table summarizes the maximum used HTTP techniques:

GET: The GET method requests a illustration of the desired resource. Requests the use of GET have to best retrieve records and have to have no other effect.
POST: The POST technique requests that the server accept the records enclosed in the request as a new object/entity of the resource recognized by the URI.
PUT: The PUT technique requests that the server take delivery of the statistics enclosed inside the request as a modification to current item identified via the URI. If it does no longer exist then PUT approach have to create one.
DELETE: The DELETE approach requests that the server delete the required resource.
These are the maximum commonplace HTTP techniques.

Angular JS Interview Questions
Question 13. What Is Koa.Js Request Object?

Answer :

A Koa Request item is an abstraction on pinnacle of node's vanilla request item, imparting additional capability this is useful for every day HTTP server development. The Koa request item is embeded within the context object, this. Lets sign off the request object each time we get a request:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var _ = router();
_.Get('/hi there', getMessage);
function *getMessage()
    console.Log(this.Request);
    this.Body = 'Your request has been logged.';

app.Use(_.Routes());
app.Listen(3000);

ReactJS Tutorial
Question 14. What Is Koa.Js Response Object?

Answer :

A Koa Response item is an abstraction on pinnacle of node's vanilla reaction item, offering extra capability that is beneficial for every day HTTP server improvement. The Koa reaction object is embeded within the context item, this. Lets sign off the reaction item on every occasion we get a request:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var _ = router();
_.Get('/hello', getMessage);
characteristic *getMessage()
    this.Frame = 'Your request has been logged.';
    console.Log(this.Response);

app.Use(_.Routes());
app.Pay attention(3000);

Question 15. What Is Koa.Js Redirects?

Answer :

Redirection is very critical whilst creating web sites. If a malformed URL is requested or there are some mistakes for your server, you need to redirect them to the respective blunders pages. Redirects can also be used to maintain humans out of restricted regions of your website. Let us create an errors web page and redirect to that web page whenever a person requests a malformed URL:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var _ = router();
_.Get('/not_found', printErrorMessage);
_.Get('/hi there', printHelloMessage);
app.Use(_.Routes());
app.Use(handle404Errors);
characteristic *printErrorMessage()
    this.Fame = 404;
    this.Frame = "Sorry we do not have this resource.";

characteristic *printHelloMessage()
    this.Reputation = 2 hundred;
    this.Body = "Hey there!";

characteristic *handle404Errors(next)
  if (404 != this.Reputation) go back;
  this.Redirect('/not_found');

app.Concentrate(3000);

When we run this code and navigate to any path apart from /hi there, we will be redirected to /not_found. We have located the middleware on the give up(app.Use function call to this middleware). This ensures we attain the middleware at last and send the corresponding reaction.

D3.Js Interview Questions
Question 16. What Is Koa.Js Error Handling?

Answer :

Error coping with plays an crucial part in building web packages. Koa uses middlewares for this cause as well.

In koa you add a middleware that does strive  yield next  as one of the first middleware. If we come across any error downstream, we return to the related catch clause and handle the error right here.

Backbone.Js Tutorial
Question 17. What Is Cascading In Koa.Js?

Answer :

Middleware functions are features that have get entry to to the context object and the following middleware feature within the software’s request-response cycle. These functions are used to adjust request and response items for responsibilities like parsing request bodies, adding response headers, etc. Koa goes a step in addition by means of yielding 'downstream', then flowing control back 'upstream'. This effect is known as cascading.

KnockoutJS Interview Questions
Question 18. What Is Order Of Middleware Calls?

Answer :

One of the maximum essential things about middleware in koa is that the order wherein they're written/protected on your file, are the order in which they're done downstream. As soon as we hit a yield announcement in a middleware, it switches to the following middleware in line until we reach the closing. Then again we start moving again up and resuming features from yield statements.

For instance, within the following code snippet, the primary function executes first till yield, then the second middleware till yield, then the third. As we haven't any extra middlewares here, we begin moving back up, executing in reverse order, ie, 0.33, 2nd, first.

Ext JS Interview Questions
Question 19. What Is Third Party Middleware?

Answer :

A listing of Third party middleware for express is available right here. Following are a number of the maximum generally used middlewares:

koa-bodyparser
koa-router
koa-static
koa-compress
KnockoutJS Tutorial
Question 20. What Is Koa.Js Templating?

Answer :

Pug is a templating engine. Templating engines are used to get rid of the cluttering of our server code with HTML, concatenating strings wildly to current HTML templates. Pug is a very effective templating engine which has a variety of features together with filters, includes, inheritance, interpolation, and so on. There is lots of floor to cowl on this.

To use Pug with koa, we want to install it,

$ npm install --save pug koa-pug
Now that pug is established, set it as the templating engine in your app. Add the subsequent code for your app.Js report.
Var koa = require('koa');
var router = require('koa-router');
var app = koa();
var Pug = require('koa-pug');
var pug = new Pug(
  viewPath: './views',
  basedir: './views',
  app: app //Equivalent to app.Use(pug)
);
var _ = router(); //Instantiate the router
app.Use(_.Routes()); //Use the routes described using the router
app.Pay attention(3000);

Now create a brand new listing called perspectives. Inside that create a record referred to as first_view.Pug, and input the subsequent records in it.

Doctype html
html
    head
        title="Hello Pug"
    frame
        p.Greetings#humans Hello Views!
To run this page, add the following course in your app:
_.Get('/hello', getMessage); // Define routes
characteristic *getMessage()
    this.Render('first_view');
;

ExpressJS Interview Questions
Question 21. What Is Attributes?

Answer :

To define attributes, we use a comma seperated listing of attributes, in paranthesis. Class and ID attributes have special representations. The following line of code covers defining attributes, lessons and id for a given html tag.

Div.Field.Column.Fundamental#department(width="one hundred",peak="one hundred")

This line of code, get transformed to:

<div class="container column main" id="division" width="100" height="100"></div>

Question 22. How To Passing Values To Templates?

Answer :

When we render a pug template, we will absolutely skip it a cost from our path handler, which we can then use in our template. Create a new path handler with the subsequent:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var Pug = require('koa-pug');
var pug = new Pug(
  viewPath: './views',
  basedir: './views',
  app: app // equals to pug.Use(app) and app.Use(pug.Middleware)
);
var _ = router(); //Instantiate the router
_.Get('//dynamic_view', dynamicMessage); // Define routes
characteristic *dynamicMessage()
    this.Render('dynamic', 
        name: "TutorialsPoint", 
        url:"https://www.Tutorialspoint.Com"
    );
;
app.Use(_.Routes()); //Use the routes defined the usage of the router
app.Listen(3000);

ExpressJS Tutorial
Question 23. What Is Include And Components?

Answer :

Pug provides a completely intuitive way to create additives for an internet page. For example, in case you see a news internet site, the header with emblem and classes is constantly fixed. Instead of copying that to evey view we create we are able to use an encompass. Following example suggests how we can use an consist of:

Create 3 views with the following code:

HEADER.PUG

div.Header.

I'm the header for this internet site.

CONTENT.PUG

html
    head
        identify Simple template
    frame
        consist of ./header.Pug
        h3 I'm the principle content
        consist of ./footer.Pug

FOOTER.PUG

div.Footer.

    I'm the footer for this website.

Create a path for this as follows:

var koa = require('koa');
var router = require('koa-router');
var app = koa();
var Pug = require('koa-pug');
var pug = new Pug(
  viewPath: './perspectives',
  basedir: './views',
  app: app //Equivalent to app.Use(pug)
);
var _ = router(); //Instantiate the router
_.Get('/components', getComponents);
function *getComponents()
    this.Render('content material.Pug');

app.Use(_.Routes()); //Use the routes defined using the router
app.Pay attention(3000);

Require Js Interview Questions
Question 24. What Is Koa.Js Form Data?

Answer :

Forms are an intergral part of the web. Almost every internet site we go to offers us bureaucracy that post or fetch some facts for us. To get commenced with forms, we are able to first set up the koa-frame To install this, visit your terminal and use:

$ npm deploy --store koa-frame
Replace your app.Js report contents with the following code:
var koa = require('koa');
var router = require('koa-router');
var bodyParser = require('koa-frame');
var app = koa();
//Set up Pug
var Pug = require('koa-pug');
var pug = new Pug(
  viewPath: './perspectives',
  basedir: './perspectives',
  app: app //Equivalent to app.Use(pug)
);
//Set up body parsing middleware
app.Use(bodyParser(
    ambitious:uploadDir: './uploads',
    multipart: actual,
    urlencoded: actual
));
_.Get('/', renderForm);
_.Post('/', handleForm);
function * renderForm()
    this.Render('shape');

feature *handleForm()
    console.Log(this.Request.Frame);
    console.Log(this.Req.Frame);
    this.Frame = this.Request.Body; //This is in which the parsed request is stored

app.Use(_.Routes()); 
app.Pay attention(3000);

Node.Js Interview Questions
Question 25. What Is Koa.Js File Uploading?

Answer :

Web applications want to provide the functionality to permit report uploads. Let us see how we are able to obtain documents from the customers and save them on our server.

We have already used the koa-body middleware for parsing requests. This middleware is also used for dealing with report uploads. Let us create a shape that allows us to upload documents and then store those files the usage of koa. First create a template known as file_upload.Pug with the following contents:

html
    head
        title File uploads
    frame
        shape(movement="/upload" method="POST" enctype="multipart/form-data")
            div
                input(kind="text" call="call" placeholder="Name")
            div
                input(kind="file" call="photograph")
            div
                enter(kind="put up")




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