Quiz about Certification Exam, Salesforce, Salesforce-JavaScript-Developer-I

Question 1

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 alert ( ‘Hey! I am John Doe’) ; 
03 button.addEventListener (‘click’, listen); 
Which two code lines make this code work as required? 
Choose 2 answers

Accepted Answer

On line 04, use button.removeEventListener(‘ click” , listen);

Accepted Answer

On line 06, add an option called once to button.addEventListener().

Answer

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

Answer

On line 04, use event.stopPropagation ( ),

Question 2

Refer to the code below:  01 const exec = (item, delay) =>{ 
02 new Promise(resolve => setTimeout( () => resolve(item), delay)), 
03 async function runParallel() { 
04 Const (result1, result2, result3) = await Promise.all{ 
05 [exec (‘x’, ‘100’) , exec(‘y’, 500), exec(‘z’, ‘100’)] 
06 ); 
07 return `parallel is done: $(result1) $(result2)$(result3)`; 
08 } 
} 
} 
Which two statements correctly execute the runParallel () function? 
Choose 2 answers

Accepted Answer

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

Accepted Answer

runParallel () .then(function(data) return data

Answer

Async runParallel () .then(data);

Answer

runParallel () .then(data);

Question 3

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 the function?

Choose 2 answers

Accepted Answer

console.assert(sum3(1, ‘2’)) == 12);

Accepted Answer

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

Answer

console.assert(sum3(0)) == 0);

Answer

console.assert(sum3(‘hello’, 2, 3, 4)) === NaN);

Question 4

Which statement phrases successfully?

Accepted Answer

JSON.parse(‘ “ foo ” ’);

Answer

JSON.parse ( ‘ foo ’ );

Answer

JSON.parse ( “ foo ” );

Answer

JSON.parse( “ ‘ foo ’ ” );

Question 5

Refer to the code below:  01 let car1 = new promise((_, reject) => 
02 setTimeout(reject, 2000, “Car 1 crashed in”)); 
03 let car2 = new Promise(resolve => setTimeout(resolve, 1500, “Car 2 
completed”)); 
04 let car3 = new Promise(resolve => setTimeout (resolve, 3000, “Car 3 
Completed”)); 
05 Promise.race([car1, car2, car3]) 
06 .then(value => ( 
07 let result = $(value) the race. `; 
08 )) 
09 .catch( arr => ( 
10 console.log(“Race is cancelled.”, err); 
11 )); 
What is the value of result when Promise.race executes?

Accepted Answer

Car 2 completed the race.

Answer

Car 3 completed the race.

Answer

Car 1 crashed in the race.

Answer

Race is cancelled.

Question 6

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 require an import 
2. Logs an error when the boolean statement evaluates to false 
3. Works in both the browser and Node.js 
Which meet the requirements?

Accepted Answer

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

Answer

assert (number % 2 === 0);

Answer

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

Answer

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

Question 7

A developer is working on an ecommerce website where the delivery date is dynamically  calculated based on the current day. The code line below is responsible for this calculation. 
Const deliveryDate = new Date (); 
Due to changes in the business requirements, the delivery date must now be today’s 
date + 9 days. 
Which code meets this new requirement?

Accepted Answer

deliveryDate.setDate(( new Date ( )).getDate () +9);

Answer

deliveryDate.setDate( Date.current () + 9);

Answer

deliveryDate.date = new Date(+9) ;

Answer

deliveryDate.date = Date.current () + 9;

Question 8

Which three statements are true about promises ?  Choose 3 answers

Accepted Answer

A Promise has a .then() method.

Accepted Answer

A fulfilled or rejected promise will not change states .

Accepted Answer

A pending promise can become fulfilled, settled, or rejected.

Answer

The executor of a new Promise runs automatically.

Answer

A settled promise can become resolved.

Question 9

Given the code below:  01 function GameConsole (name) { 
02 this.name = name; 
03 } 
04 
05 GameConsole.prototype.load = function(gamename) { 
06 console.log( ` $(this.name) is loading a game : $(gamename) …`); 
07 ) 
08 function Console 16 Bit (name) { 
09 GameConsole.call(this, name) ; 
10 } 
11 Console16bit.prototype = Object.create ( GameConsole.prototype) ; 
12 //insert code here 
13 console.log( ` $(this.name) is loading a cartridge game : $(gamename) …`); 
14 } 
15 const console16bit = new Console16bit(‘ SNEGeneziz ’); 
16 console16bit.load(‘ Super Nonic 3x Force ’); 
What should a developer insert at line 15 to output the following message using the 
method ? 
> SNEGeneziz is loading a cartridge game: Super Monic 3x Force . . .

Accepted Answer

Console16bit.prototype.load = function(gamename) {

Answer

Console16bit.prototype.load(gamename) = function() {

Answer

Console16bit = Object.create(GameConsole.prototype).load = function (gamename) {

Answer

Console16bit.prototype.load(gamename) {

Question 10

A developer has the following array of student test grades:  Let arr = [ 7, 8, 5, 8, 9 ]; 
The Teacher wants to double each score and then see an array of the students 
who scored more than 15 points. 
How should the developer implement the request?

Accepted Answer

Let arr1 = arr.map((num) => num*2). Filter (( val) => val > 15);

Answer

Let arr1 = arr.filter(( val) => ( return val > 15 )) .map (( num) => ( return num *2 ))

Answer

Let arr1 = arr.mapBy (( num) => ( return num *2 )) .filterBy (( val ) => return val > 15 )) ;

Answer

Let arr1 = arr.map((num) => ( num *2)).filterBy((val) => ( val >15 ));

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