Question 1

A developer is setting up a new Node.js server with a client library that is built using events and

callbacks.

The library:

- Will establish a web socket connection and handle receipt of messages to the server

- Will be imported with `require`, and made available with a variable called `ws`.

The developer also wants to add error logging if a connection fails.

Given this information, which code segment shows the correct way to set up a client with two events

that listen at execution time?

Aws.connect(() => {
console.log('Connected to client');
}).catch((error) => {
console.log('ERROR', error);
});

Bws.on('connect', () => {
console.log('Connected to client');
});
ws.on('error', (error) => {
console.log('ERROR', error);
});

Cws.on('connect', () => {
console.log('Connected to client');
});
ws.on('error', (error) => {
console.log('ERROR', error);
});

Dtry {
ws.connect(() => {
console.log('Connected to client');
});
} catch(error) {
console.log('ERROR', error);
}

Answer : B, C

Question 2

Refer to the following array:

```javascript

let arr = [1, 2, 3, 4, 5];

```

Which two lines of code result in a second array, `arr2`, created such that `arr2` is a reference to

`arr`?

Choose 2 answers

Alet arr2 = arr.slice(0, 5);

Blet arr2 = Array.from(arr);

Clet arr2 = arr;

Dlet arr2 = arr.sort();

Answer : C, D

Question 3

Given the code:

01 function GameConsole(name) {

02 this.name = name;

03 }

05 GameConsole.prototype.load = function(gamename) {

06 console.log('${this.name} is loading a game: ${gamename}....');

07 }

09 function Console16bit(name) {

10 GameConsole.call(this, name);

11 }

13 Console16bit.prototype = Object.create(GameConsole.prototype);

15 // insert code here

16 console.log('${this.name} is loading a cartridge game: ${gamename}....');

17 }

19 const console16bit = new Console16bit('SNEGeneziz');

20 console16bit.load('Super Monic 3x Force');

What should a developer insert at line 15?

AConsole16bit = Object.create(GameConsole.prototype).load = function(gamename) {

BConsole16bit.prototype.load(gamename) = function() {

CConsole16bit.prototype.load(gamename) {

DConsole16bit.prototype.load = function(gamename) {

Answer : D

________________________________________

Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

A subclass created by:

Console16bit.prototype = Object.create(GameConsole.prototype);

inherits all prototype methods from GameConsole, including load.

To override the inherited method, the correct syntax is to assign a new function to the method name on the prototype:

Console16bit.prototype.load = function(gamename) {

console.log(`${this.name} is loading a cartridge game: ${gamename}....`);

};

Why the other options are wrong:

A assigns something to the constructor function itself, not to the prototype method. Invalid.

B attempts to call a function in the left-hand side of an assignment; invalid syntax.

C also uses invalid syntax---prototype methods cannot be defined this way.

D is the correct definition of a prototype method override.

________________________________________

JavaScript Knowledge Reference (text-only)

Methods are overridden by assigning functions to Subclass.prototype.methodName.

Object.create() establishes prototype inheritance.

Constructor functions require prototype method attachment using assignment syntax.

==================================================

Question 4

A developer wants to set up a secure web server with Node.js. The developer creates a directory locally called app-server, and the first file is app-server/index.js.

Without using any third-party libraries, what should the developer add to index.js to create the secure web server?

Aconst server = require('secure-server');

Bconst tls = require('tls');

Cconst http = require('http');

Dconst https = require('https');

Answer : D

________________________________________

Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

Node.js provides two built-in modules for creating servers:

http creates non-secure HTTP servers

https creates secure HTTPS servers

A secure server requires:

SSL/TLS certificates (key and cert)

The built-in Node.js module designed to handle these: https

Syntax for a secure server:

const https = require('https');

const fs = require('fs');

const options = {

key: fs.readFileSync('key.pem'),

cert: fs.readFileSync('cert.pem')

};

https.createServer(options, (req, res) => {

res.write('Secure Server');

res.end();

}).listen(443);

Evaluation of options:

A is incorrect: No built-in module named secure-server exists.

B is incorrect: tls provides low-level TLS sockets, not HTTP/HTTPS servers.

C is incorrect: http only creates an insecure server.

D is correct: https is the built-in module required for secure web servers.

________________________________________

JavaScript Knowledge Reference (text-only)

Node.js exposes built-in modules http and https for server creation.

Secure servers require the https module, which supports TLS/SSL.

The tls module is lower-level and not used for full HTTP servers.

==================================================

Question 5

Refer to the code:

01 console.log('Start');

02 Promise.resolve('Success').then(function(value) {

03 console.log('Success');

04 });

05 console.log('End');

What is the output after the code executes successfully?

AStart
Success
End

BStart
End
Success

CEnd
Start
Success

DSuccess
Start
End

Answer : B

________________________________________

Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

console.log('Start') runs immediately (synchronous).

Promise.resolve().then(...) places the callback in the microtask queue. The .then handler does not run immediately.

console.log('End') runs next (still synchronous).

After the synchronous script finishes, the microtask queue runs, logging 'Success'.

Execution order:

Start

End

Success

This matches option B.

________________________________________

JavaScript Knowledge Reference (text-only)

Promise .then() callbacks execute after the current call stack finishes (microtask queue).

Synchronous logs run immediately, before promise callbacks.

==================================================

Free Salesforce Certified JavaScript Developer (JS-Dev-101) Practice Questions

Salesforce JS-Dev-101 Sample Exam Questions

Question 1

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