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JavaScript-Developer-I 無料問題集「Salesforce Certified JavaScript Developer I」

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トータル 224 問

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質問 1

A developer is debugging a web server that uses Node.js The server hits a runtimeerror every third request to an important endpoint on the web server.
The developer added a break point to the start script, that is at index.js at he root of the server's source code. The developer wants to make use of chrome DevTools to debug.
Which command can be run to access DevTools and make sure the breakdown is hit ?

（A）Node --inspect-brk index.js

（B）Node inspect index.js

（C）node -i index.js

（D）Node --inspect index.js

正解：D 解答を投票する

質問 2

Refer to the code below:
Function changeValue(obj) {
Obj.value = obj.value/2;
}
Const objA = (value: 10);
Const objB = objA;
changeValue(objB);
Const result = objA.value;
What is the value of result after the code executes?

（A）Undefined

（B）5

（C）10

（D）Nan

正解：B 解答を投票する

質問 3

Refer to code below:
Let a ='a';
Let b;
// b = a;
console.log(b);
What is displayed when the code executes?

（A）Undefined

（B）Null

（C）ReferenceError: b is not defined

（D）A

正解：A 解答を投票する

質問 4

Given the JavaScript below:
01 function filterDOM (searchString) {
02 const parsedSearchString = searchString && searchString.toLowerCase() ;
03 document.quesrySelectorAll(' .account' ) . forEach(account => (
04 const accountName = account.innerHTML.toLOwerCase();
05 account. Style.display = accountName.includes(parsedSearchString) ? /*Insert code*/;
06 )};
07 }
Which code should replace the placeholder comment on line 05 to hide accounts that do not match thesearch string?

（A）' name ' : ' block '

（B）' hidden ' : ' visible '

（C）' Block ' : ' none '

（D）' visible ' : ' hidden '

正解：C 解答を投票する

質問 5

Refer to the code below:
const event = new CustomEvent(
//Missing Code
);
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

（A）{ type : 'update', recordId : '123abc' }

（B）'Update' , (recordId : '123abc'(

（C）'Update' , '123abc'

（D）'Update' , {Details : {recordId : '123abc'}}

正解：B、D 解答を投票する

質問 6

Considering type coercion, what does the following expression evaluate to?
True + '13' + NaN

（A）14

（B）' true13 '

（C）' true13NaN '

（D）' 113Nan '

正解：C 解答を投票する

質問 7

Refer to the following code block:

What is the console output?

（A）> Better student Jackie got 100% on test.

（B）> Jackie got 70% on test.

（C）> Uncaught Reference Error

（D）> Better student Jackie got 70% on test.

正解：A 解答を投票する

質問 8

Refer to the code:

Given the code above, which three properties are set for pet1? Choose 3 answers

（A）type

（B）name

（C）size

（D）canTalk

（E）owner

正解：A、C、D 解答を投票する

質問 9

Universal Containers (UC) notices that its application that allows users to search for accounts makes a network request each time a key is pressed. This results in too many requests for the server to handle.
Address this problem, UC decides to implement a debounce function on string change handler.
What are three key steps to implement this debounce function?
Choose 3 answers:

（A）Ensure that the network request has the property debounce set to true.

（B）When thesearch string changes, enqueue the request within a setTimeout.

（C）If there is an existing setTimeout and the search string change, allow the existingsetTimeout to finish, and do not enqueue a new setTimeout.

（D）If there is an existing setTimeout and the search string changes, cancel the existingsetTimeout using thepersisted timerId and replace it with a new setTimeout.

（E）Store the timeId of the setTimeout last enqueued by the search string change handle.

正解：A、B、C 解答を投票する

質問 10

A developer at Universal Containers is creating their new landing pagebased on HTML, CSS, and JavaScript.
The website includes multiple external resources that are loaded when the page is opened.
To ensure that visitors have a good experience, a script named personalizeWebsiteContent needs to be executed when the webpage isloaded and there is no need to wait for the resources to be available.
Which statement should be used to call personalizeWebsiteContent based on the above business requirement?

（A）windows,addEventListener('onload', personalizeWebsiteContent);

（B）windows,addEventListener('DOMContent Loaded ', personalizeWebsiteContent);

（C）windows,addEventListener('onDOMCContentLoaded', personalizeWebsiteContent);

（D）windows,addEventListener('load', personalizeWebsiteContent);

正解：D 解答を投票する

質問 11

Refer to code below:
Let first = 'who';
Let second = 'what';
Try{
Try{
Throw new error('Sad trombone');
}catch (err){
First ='Why';
}finally {
Second ='when';
} catch (err) {
Second ='Where';
}
What are the values for first and second once the code executes ?

（A）First is why and second is when

（B）First is Who and second is When

（C）First is why and second is where

（D）First is who and second is where

正解：A 解答を投票する

質問 12

A developer has a web server running with Node.js. The command to start the web server is node server.js.
The web server started having
latency issues. Instead of a one second turnaround for web requests, the developer now sees a five second turnaround.
Which command can the web developer run to see what the module is doing during the latency period?

（A）DEBUG=http, https node server.js

（B）NODE_DEBUG=true node server.js

（C）DEBUG=true node server.js

（D）NODE_DEBUG=http,https node server.js

正解：C 解答を投票する

質問 13

A developer wrote the following code to test a sum3 function that takes in an array of numbers and returns the sum of the first three numbers in the array, and the test passes.
A different developer made changes to the behavior of sum3 to instead sum only the first two numbers present in the array.

Which two results occur when running this test on the updated sum3 function?
Choose 2 answers

（A）The line 02 assertion fails.

（B）The line 05 assertion fails.

（C）The line 02 assertion passes.

（D）The line 05 assertion passes.

正解：B、C 解答を投票する

質問 14

Refer to the code below
let inArray = [[1,2],[3,4,5]];
which two statements results in the array [1,2,3,4,5]?
choose 2 answer

（A）[ ].concat.apply(inArray,[ ]);

（B）[ ].concat.apply([ ],inArray);

（C）[ ].concat(...inArray);

（D）[ ].concat([...inArray])

正解：B、C 解答を投票する

質問 15

Refer to the string below:
const str = 'Salesforce';
Which two statements result in the word 'Sales'?
Choose 2 answers

（A）str.substring (1, 5);

（B）str.substring (0, 5);

（C）str.substr (0, 5);

（D）str.substr(1, 5);

正解：B、C 解答を投票する

質問 16

A developer uses a parsed JSON string to work with user information as in the block below:
01 const userInformation ={
02 " id " : "user-01",
03 "email" : "[email protected]",
04 "age" : 25
Which two options access the email attribute in the object?
Choose 2 answers

（A）userInformation(email)

（B）userInformation("email")

（C）userInformation.email

（D）userInformation.get("email")

正解：B、C 解答を投票する

質問 17

Refer to the code below:
Let str = 'javascript';
Str[0] = 'J';
Str[4] = 'S';
After changing the string indexvalues, the value of str is 'javascript'. What is the reason for this value:

（A）Primitive values are mutable.

（B）Non-primitive values are immutable.

（C）Non-primitive values are mutable.

（D）Primitive values are immutable.

正解：D 解答を投票する

質問 18

bar, awesome is a popular JavaScript module. the versions publish to npm are:

Teams at Universal Containers use this module in a number of projects. A particular project has thepackage, json definition below.

A developer runs this command: npm install.
Which version of bar .awesome is installed?

（A）1.3.5

（B）1.3.1

（C）The command fails, because version 130 is not found

（D）1.4.0

正解：A 解答を投票する

質問 19

A developer wants to use a try...catch statement to catch any error that countSheep () may throw and pass it to a handleError () function.
What is the correct implementation of the try...catch?

（A）