Salesforce Certified JavaScript Developer 問題練習

Question No : 1
Given the code below:
const copy = JSON.stringify([ newString(‘ false ’), new Bollean( false ), undefined ]);
What is the value of copy?

• A.-- [ \”false\”, { } ]--
• B.-- [ false, { } ]--
• C.-- [ \”false\”, false, undefined ]--
• D.-- [ \”false\”,false, null ]--

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Question No : 2
Which code statement below correctly persists an objects in local Storage?

• A.const setLocalStorage = (storageKey, jsObject) => {window.localStorage.setItem(storageKey, JSO
• B.stringify(jsObject));}
• C.const setLocalStorage = (jsObject) => {window.localStorage.connectObject(jsObject));}
• D.const setLocalStorage= (jsObject) => {window.localStorage.setItem(jsObject);}
• E.const setLocalStorage = (storageKey, jsObject) => {window.localStorage.persist(storageKey, jsObject);}

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Question No : 3
Refer to the following code:
function test (val) {
If (val === undefined) {
return ‘Undefined values!’ ;
}
if (val === null) {
return ‘Null value! ’;
}
return val;
}
Let x;
test(x);
What is returned by the function call on line 13?

• A.Undefined
• B.Line 13 throws an error.
• C.‘Undefined values!’
• D.‘Null value!’

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Question No : 4
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 boost with an event?

• A.Server.catch ((server) => { console.log(‘ERROR’, error); });
• B.Server.error ((server) => { console.log(‘ERROR’, error); });
• C.Server.on (‘error’, (error) => { console.log(‘ERROR’, error); });
• D.Try{ server.start(); } catch(error) { console.log(‘ERROR’, error); }

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Question No : 5
Refer to the following code that imports a module named utils:
import (foo, bar) from ‘/path/Utils.js’;
foo() ;
bar() ;
Which two implementations of Utils.js export foo and bar such that the code above runs without error? Choose 2 answers

• A.// FooUtils.js and BarUtils.js exist Import (foo) from ‘/path/FooUtils.js’; Import (boo) from ‘ /path/NarUtils.js’;
• B.const foo = () => { return ‘foo’ ; } const bar = () => { return ‘bar’ ; } export { bar, foo }
• C.Export default class { foo() { return ‘foo’ ; } bar() { return ‘bar’ ; } }
• D.const foo = () => { return ‘foo’;} const bar = () => {return ‘bar’; } Export default foo, bar;

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Question No : 6
What is the result of the code block?

• A.The console logs only ‘flag’.
• B.The console logs ‘flag’ and another flag.
• C.An error is thrown.
• D.The console logs ‘flag’ and then an error is thrown.

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Question No : 7
Refer to the code below:
letsayHello = () => {
console.log (‘Hello, world!’);
};
Which code executes say Hello once, two minutes from now?

• A.setTimeout(sayHello, 12000);
• B.setInterval(sayHello, 12000);
• C.setTimeout(sayHello(), 12000);
• D.delay(sayHello, 12000);

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Question No : 8
A developer has the function, shown below, that is called when a page loads.
function onload() {
console.log(“Page has loaded!”);
}
Where can the developer see the log statement after loading the page in the browser?

• A.Terminal running the web server.
• B.Browser performance toots
• C.Browser javaScript console
• D.On the webpage.

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Question No : 9
The developer has a function that prints “Hello” to an input name.
To test this,thedeveloper created a function that returns “World”. However the following snippet does not print “Hello World”.



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

• A.Change line 7 to) ();
• B.Change line 2 to console.log(‘Hello’,name() );
• C.Change line 9 to sayHello(world) ();
• D.Change line 5 to function world () {

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Question No : 10
A developer has code that calculates a restaurant bill, but generates incorrect answers while testing the code:
function calculateBill (items) {
let total = 0;
total += findSubTotal(items);
total += addTax(total);
total += addTip(total);
return total;
}
Which option allows the developer to step into each function execution within calculateBill?

• A.Using the debugger command on line 05.
• B.Using the debugger command on line 03
• C.Calling the console.trace (total) method on line 03.
• D.Wrapping findSubtotal in a console.log() method.

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Question No : 11
A developer wrote a fizzbuzz function that when passed in a number, returns the following:
● ‘Fizz’ if the number is divisible by 3.
● ‘Buzz’ if the number is divisible by 5.
● ‘Fizzbuzz’ if the number is divisible by both 3 and 5.
● Empty string if the number is divisible by neither 3 or 5.
Which two test cases will properly test scenarios for the fizzbuzz function? Choose 2 answers

• A.let res = fizzbuzz(5);console.assert (res === ‘ ’ );
• B.let res = fizzbuzz(15);console.assert (res === ‘ fizzbuzz ’ )
• C.let res = fizzbuzz(Infinity);console.assert (res === ‘ ’ )
• D.let res = fizzbuzz(3);console.assert (res === ‘ buzz ’ )

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Question No : 12
Considering type coercion, what does the following expression evaluate to?
True + ‘13’ + NaN

• A.‘ 113Nan ’
• B.14
• C.‘ true13 ’
• D.‘ true13NaN ’

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Question No : 13
Refer to the HTML below:
<div id=”main”>
<ul>
<li>Leo</li>
<li>Tony</li>
<li>Tiger</li>
</ul>
</div>
Which JavaScript statement results in changing “ Tony” to “Mr. T.”?

• A.document.querySelectorAll(‘$main $TONY’).innerHTML = ’ Mr.
• B.’;
• C.document.querySelector(‘$main li:second-child’).innerHTML = ’ Mr.
• D.’;
• E.document.querySelector(‘$main li.Tony’).innerHTML = ’ Mr.
• F.’;
• G.document.querySelector(‘$main li:nth-child(2)’),innerHTML =’ Mr.
• H.’;

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Question No : 14
Which two code snippets show working examples of a recursive function? Choose 2 answers

• A.Let countingDown = function(startNumber) { If ( startNumber >0) { console.log(startNumber) ; return countingDown(startNUmber); } else { return startNumber; }};
• B.Function factorial ( numVar ) { If (numVar < 0) return; If ( numVar === 0 ) return 1; return numVar -1;
• C.Const sumToTen = numVar => { If (numVar < 0) Return; return sumToTen(numVar + 1)};
• D.Const factorial =numVar => { If (numVar < 0) return; If ( numVar === 0 ) return 1; return numVar * factorial ( numVar - 1 ); };

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Question No : 15
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 fora button with class= “blue”. The test fails because no such button is found.
Which type of test category describes this test?

• A.True positive
• B.True negative
• C.False positive
• D.False negative

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