Prepare for Salesforce JavaScript Developer I Certification - Mock Test 3

Question 1 of 20

Universal Containers recently launched its new landing page to host a crowdfunding campaign. The page uses an external library to display some third-party ads. Once the page is fully loaded, it creates more than 50 new HTML items placed randomly inside the DOM, like the one in the code below:

<div class='ad-library-item ad-hidden' onload='myFunction()'>
<img src='/ad-library/ad01.gif' />
</div>

All the elements include the same `ad-library-item` class. They are hidden by default, and they are randomly displayed while the user navigates through the page. Tired of all the ads, what can the developer do to temporarily and quickly remove them?

Choose 1 answer

A. Use the DOM inspector to remove all the elements containing the class `ad-library-item`.

B. Use the browser console to execute a script that removes all the elements containing the class `ad-library-item`.

C. Use the DOM inspector to prevent the `load` event from being fired.

D. Use the browser console to execute a script that prevents the `load` event from being fired.

Question 2 of 20

A developer removes the HTML class attribute from the checkout button, so now it is simply:

<button>Checkout</button>

There is a test to verify the existence of the checkout button; however, it looks for a button with `class="blue"`. The test fails because no such button is found. Which type of test category describes this test?

Choose 1 answer

A. True positive

B. False positive

C. False negative

D. True negative

Question 3 of 20

A developer wants to use a module called `DatePrettyPrint`. This module exports one default function called `printDate()`. How can a developer import and use the `printDate()` function?

Choose 1 answer

A.

import DatePrettyPrint from '/path/DatePrettyPrint.js';
DatePrettyPrint.printDate();

B.

import DatePrettyPrint() from '/path/DatePrettyPrint.js';
printDate();

C.

import printDate from '/path/DatePrettyPrint.js';
printDate();

D.

import printDate from '/path/DatePrettyPrint.js';
DatePrettyPrint.printDate();

Question 4 of 20

Refer to the code below:

01 const exec = (item, delay) =>
02   new Promise(resolve => setTimeout(() => resolve(item), delay));
03
04 async function runParallel() {
05   const [result1, result2, result3] = await Promise.all([
06     exec('x', 100),
07     exec('y', 500),
08     exec('z', 1000)
09   ]);
10   return `parallel is done: ${result1} ${result2} ${result3}`;
11 }

Which two statements correctly execute the `runParallel()` function?

Choose 2 answers

A. runParallel().done(function (data) {
  return data;
});

B. runParallel().then(data => {
  return data;
});

C. runParallel().then(function (data) {
  return data;
});

D. runParallel().then(data);

Question 5 of 20

Refer to the code below:

01 x = 3.14;
02
03 function myFunction () {
04   'use strict';
05   y = x;
06 }
07
08 z = x;
09 myFunction();

Considering the implications of 'use strict' on line 04, which three statements describe the execution of the code?

Choose 3 answers

A. 'use strict' is hoisted, so it has an effect on all lines.

B. z is equal to 3.14.

C. Line 05 throws an error.

D. 'use strict' has an effect between line 04 and the end of the file.

E. 'use strict' has an effect only on line 05.

Question 6 of 20

A developer is creating a simple webpage with a button. When a user clicks this button for the first time, a message is displayed. The developer wrote the JavaScript code below, but something is missing. The message gets displayed every time a user clicks the button, instead of just the first time.

01 function listen (event) {
02  
03   alert('Hey! I am John Doe');
04 
05 }
06 button.addEventListener('click', listen);

Which two code lines make this code work as required?

Choose 2 answers

A. On line 04, use

button.removeEventListener('click', listen);

B. On line 02, use event.first to test if it is the first execution. On line 04, use

event.stopPropagation();

C. On line 06, add an option called once to

button.addEventListener()

D. On line 04, use

button.removeEventListener('click', listen);

Question 7 of 20

Refer to the code below:

01 let o = 1;
02 get js() {
03   let city1 = String('St. Louis');
04   let city2 = String('New York');
05
06   return {
07     firstCity: city1.toLowerCase(),
08     secondCity: city2.toLowerCase()
09   };
10 }

What value can a developer expect when referencing

o.js.secondCity()

?

Choose 1 answer

'New York'

undefined

An error

'new york'

Question 8 of 20

Given the following code:

let x = ('15' + 10) * 2;

What is the value of `x`?

Choose 1 answer

A. 50

B. 1520

C. 35

D. 3020

Question 9 of 20

A developer creates a new web server that uses Node.js. It imports a server library that uses events and callbacks for handling server functionality. The server library is imported with `require` and is made available to the code by a variable named `server`. The developer wants to log any issues that the server has while booting up. Given the code and the information the developer has, which code logs an error at boot time with an event?

Choose 1 answer

A. 01 server.error((error) => {
02   console.log('ERROR', error);
03 });

B. 01 try {
02   server.start();
03 } catch (error) {
04   console.log('ERROR', error);
05 }

C. 01 server.catch((error) => {
02   console.log('ERROR', error);
03 });

D. 01 server.on('error', (error) => {
02   console.log('ERROR', error);
03 });

Question 10 of 20

A developer needs to test this function:

01 const sum3 = (arr) => {
02   if (!arr.length) return 0;
03   if (arr.length === 1) return arr[0];
04   if (arr.length === 2) return arr[0] + arr[1];
05   return arr[0] + arr[1] + arr[2];
06 };

Which two assert statements are valid tests for this function?

Choose 2 answers

A. console.assert(sum3(['hello', 2, 3]) === NaN);

B. console.assert(sum3([-3, 2]) === -1);

C. console.assert(sum3([0]) === 0);

D. console.assert(sum3([1, '2']) === 3);

Question 11 of 20

Refer to the code below:

let productSKU = '8675309';

A developer has a requirement to generate SKU numbers that are always 19 characters long, starting with 'sku', and padded with zeros. Which statement assigns the value 'sku0000000008675309'?

Choose 1 answer

A. productSKU = productSKU.padStart(19, '0').padStart(3, 'sku');

B. productSKU = 'sku' + productSKU.padStart(16, '0');

C. productSKU = productSKU.padEnd(16, '0').padStart(19, 'sku');

D. productSKU = productSKU.padEnd(16, '0').padStart('sku');

Question 12 of 20

A developer creates a class that represents a news story based on the requirements that a Story should have a body, author, and view count. The code is shown below:

01 class Story {
02   // Insert code here
03   this.body = body;
04   this.author = author;
05   this.viewCount = viewCount;
06 }

Which statement should be inserted in the placeholder on line 02 to allow for a variable to be set to a new instance of a story with the three attributes correctly populated?

Choose 1 answer

A. function Story(body, author, viewCount) {

B. constructor() {

C. super(body, author, viewCount);

D. constructor(body, author, viewCount) {

Question 13 of 20

Refer to the code below:

for (let number = 2; number <= 5; number += 1) {
  // Insert code statement here
}

The developer needs to insert a code statement in the location shown. The code statement has these requirements: 1. Does not require an import 2. Logs an error when the Boolean statement evaluates to false 3. Works in both the browser and Node.js Which statement meets these requirements?

Choose 1 answer

A. console.error(number % 2 === 0);

B. console.assert(number % 2 === 0);

C. assert(number % 2 === 0);

D. console.debug(number % 2 === 0);

Question 14 of 20

Which option is true about the strict mode in imported modules?

Choose 1 answer

A. Add the statement `use non-strict;` before any other statements in the module to enable non-strict mode.

B. Imported modules are in strict mode whether you declare them as such or not.

C. Add the statement `use strict = false;` before any other statements in the module to enable non-strict mode.

D. A developer can only reference `nonStrict()` functions from the imported module.

Question 15 of 20

The developer has a function that prints 'Hello' to an input name. To test this, the developer created a function that returns 'World'. However, the following snippet does not print 'Hello World':

01 const sayHello = (name) => {
02   console.log('Hello ', name);
03 };
04
05 const world = () => {
06   return 'World';
07 };
08
09 sayHello(world);

What can the developer do to change the code to print 'Hello World'?

Choose 1 answer

A. Change line 2 to console.log('Hello', name());

B. Change line 9 to sayHello(world());

C. Change line 5 to function world() {}

D. Change line 7 to return 'World';

Question 16 of 20

Refer to the code below:

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?

Choose 1 answer

A. End Start Success

B. Start End Success

C. Success Start End

D. Start Success End

Question 17 of 20

Refer to the code below:

01 const event = new CustomEvent(
02   // Missing code
03 );

04 obj.dispatchEvent(event);

A developer needs to dispatch a custom event called `update` to send information about `recordId`. Which two options could a developer insert at the placeholder in line 02 to achieve this? Choose 2 answers

Choose 2 answers

A. 'update'

B. new CustomEvent('update', { detail: { recordId: '123abc' } })

C. new CustomEvent('update', { recordId: '123abc' })

D. new CustomEvent({ type: 'update', recordId: '123abc' })

Question 18 of 20

Refer to the code below:

function createCounter() {
  let count = 0;
  return function() {
    count += 1;
    return count;
  };
}

const counter = createCounter();
const counter2 = createCounter();

console.log(counter());
console.log(counter());
console.log(counter2());
console.log(counter());

What is the output of the above code?

Choose 1 answer

A. 1, 2, 1, 3

B. 1, 2, 3, 4

C. 1, 2, 1, 2

D. 1, 1, 2, 3

Question 19 of 20

Refer to the code below:

async function fetchData() {
  return new Promise((resolve) => setTimeout(() => resolve('Data fetched'), 1000));
}

fetchData().then((data) => {
  console.log(data);
});
console.log('Fetching data...');

What is the output of the above code?

Choose 1 answer

A. Fetching data... Data fetched

B. Data fetched Fetching data...

C. Data fetched

D. Fetching data...

Question 20 of 20

Refer to the code below:

console.log('Start');

setTimeout(() => {
  console.log('Timeout 1');
}, 0);

Promise.resolve().then(() => {
  console.log('Promise 1');
});

console.log('End');

What is the output of the above code?

Choose 1 answer

A. Start End Promise 1 Timeout 1

B. Start Timeout 1 Promise 1 End

C. Start End Timeout 1 Promise 1

D. Start Promise 1 End Timeout 1

Test Set 3

Practice Test

Question 1 of 20

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Question 3 of 20

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Question 4 of 20

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Question 5 of 20

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Question 6 of 20

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