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Master JS-Dev-101: Salesforce Certified JavaScript Developer Exam Success

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Question 1

Refer to the code below:

01 funetion Person() (

02 thie. fixsttane = "Zoha'y

os}

05 Perscn.prototype = [

06 jek: x => 'Developer'

onde

09 const myFather = new Peracn():

10 const result = myFather.firstiame + ' * + myFather.jeb()

What is the value of result after line 10 executes?


Correct : A


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Question 2

01 class Student {

02 constructor(name) {

03 this._name = name;

04 }

05 displayGrade() {

06 console.log(`${this._name} got 70% on test.`);

07 }

08 }

09

10 class GraduateStudent extends Student {

11 constructor(name) {

12 super(name);

13 this._name = "Graduate Student " + name;

14 }

15 displayGrade() {

16 console.log(`${this._name} got 100% on test.`);

17 }

18 }

19 let student = new GraduateStudent("Jane");

20 student.displayGrade();

```

What is the console output?:


Correct : C


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Question 3

A developer wants to use a module named universalContainerslib and then call functions from it. How should a developer import every function from the module and then call the functions foo and bar?


Correct : A

import * as lib from '...' imports all named exports from the module into the namespace object lib.

You then call:

lib.foo();

lib.bar();

Option D correctly imports only foo and bar, not every function. The question explicitly says ''import every function... and then call foo and bar'', so A best matches.

Options B and C are invalid syntax or reference the wrong identifier.

________________________________________


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Question 4

01 function Monster() { this.name = 'hello'; };

02 const m = Monster();

What happens due to the missing new keyword?


Correct : B

________________________________________

Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

In JavaScript, when calling a constructor function without new:

const m = Monster();

the following happens:

The function executes as a normal function, not as a constructor.

Inside a regular function (in non-strict mode), this refers to the global object:

In a browser: window

So the line:

this.name = 'hello';

becomes:

window.name = 'hello';

Since Monster() does not return anything, its return value is undefined:

const m = undefined;

Therefore:

m is undefined

window.name becomes 'hello'

This matches option B.

________________________________________

JavaScript Knowledge Reference (text-only)

Calling a function without new uses the global object as this in non-strict mode.

Constructor functions must use new to create a new object.

Functions without an explicit return return undefined.


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Question 5

Refer to the code below:

01 let timedFunction = () => {

02 console.log('Timer called.');

03 };

04

05 let timerId = setInterval(timedFunction, 1000);

Which statement allows a developer to cancel the scheduled timed function?


Correct : A

Comprehensive and Detailed Explanation From JavaScript Knowledge:

The code:

let timerId = setInterval(timedFunction, 1000);

setInterval schedules timedFunction to run every 1000 ms.

It returns an interval ID (here stored in timerId), which is used to cancel the interval later.

To cancel:

Use clearInterval(timerId);

This is the standard browser (and Node.js) API:

let id = setInterval(fn, delay);

clearInterval(id); stops future executions of that interval.

Check other options:

B . removeInterval(timerId);

There is no removeInterval function in the standard JavaScript timer API.

C . removeInterval(timedFunction);

Again, no such function; and timers are cancelled by ID, not by the callback function reference.

D . clearInterval(timedFunction);

clearInterval expects the ID returned by setInterval, not the callback function.

Passing the function does not cancel the timer.

Therefore, the correct statement is:

Answe r: A

Study Guide / Concept Reference (no links):

Timer APIs: setInterval and clearInterval

Relationship between timer ID and cancellation

Difference between interval ID and callback function

Basic async timing patterns in JavaScript


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