Instant Access Salesforce.JS-Dev-101.v2026-05-21.q110 Actual Practice Test Engine for Free (Page 16)

Question 71

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 sku000000008675309?

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

Correct Answer: B

Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:
We start with:
let productSKU = '8675309';
The requirement:
Final SKU string:
Length: 19 characters.
Starts with 'sku'.
Remaining characters are digits padded with zeros on the left (to reach total length).
We can use String.prototype.padStart and String.prototype.padEnd:
str.padStart(targetLength, padString)
If str.length < targetLength, it adds padString to the start until the length is targetLength.
str.padEnd(targetLength, padString)
Similar, but adds padString to the end.
We want a pattern like:
First, pad the numeric part out to a fixed length with zeros.
Then, pad to total length with 'sku' at the start.
Analyze Option B
productSKU = productSKU.padStart(16, '0').padStart(19, 'sku');
Step 1: productSKU.padStart(16, '0')
Initial productSKU is '8675309' (length 7).
After padStart(16, '0'), we pad zeros on the left to reach length 16.
We need 16 − 7 = 9 zeros:
Result after step 1:
productSKU === '0000000008675309' // length 16
Step 2: .padStart(19, 'sku')
Now productSKU has length 16.
We call padStart(19, 'sku'):
We need 19 − 16 = 3 extra characters.
The pad string 'sku' is exactly 3 characters, so it is added as-is at the start.
Result after step 2:
productSKU === 'sku0000000008675309' // length 19
This satisfies:
Length 19.
Starts with 'sku'.
Remaining characters are zeros plus the original digits, i.e. a zero-padded numeric section.
While the literal sample sku000000008675309 in the text has a slightly different count of zeros, Option B follows the requirement pattern:
3 characters of 'sku'
Numeric part padded with zeros to make 16 characters total for the numeric part
3 + 16 = 19 total characters
Option B matches the intended logic using padStart and padEnd.
Why the other options are incorrect
Option A:
productSKU = productSKU.padEnd(16, '0').padStart('sku');
padEnd(16, '0') produces '8675309000000000' (original number followed by zeros).
padStart('sku') is invalid usage:
padStart takes a numeric target length as the first argument, not a string.
Passing 'sku' as the first argument leads to type coercion that does not achieve the intended behavior.
This will not reliably produce the desired SKU.
Option C:
productSKU = productSKU.padEnd(16, '0').padStart(19, 'sku');
First padEnd(16, '0') from '8675309' gives '8675309000000000' (length 16, zeros at the end).
Then padStart(19, 'sku') adds 3 chars 'sku' at the front:
Result: 'sku8675309000000000'.
This string starts with 'sku', but the zeros are at the end of the digits, not padding the numeric part on the left as desired.
Option D:
productSKU = productSKU.padStart(19, '0').padStart('sku');
First padStart(19, '0') pads zeros at the left to make the length 19.
Then padStart('sku') again incorrectly uses a string where a numeric targetLength is required.
This will not produce the correct SKU format.
Therefore, the only option that correctly uses padStart to create a 16-character zero-padded numeric portion and then a 19-character string starting with 'sku' is:
Reference / Study Guide concepts (no links):
String.prototype.padStart(targetLength, padString)
String.prototype.padEnd(targetLength, padString)
String length calculations
Left-padding numeric strings with zeros
Building prefixed identifiers with fixed total length

Question 72

Refer to the code below:
01 const server = require('server');
02
03 // Insert code here
A developer imports a library that creates a web server. The imported library uses events and callbacks to start the server.
Which code should be inserted at line 03 to set up an event and start the web server?

A.server.on('connect', (port) => { console.log('Listening on', port); });
B.server.start();
C.server((port) => { console.log('Listening on', port); });
D.server();

Question 73

Refer to the code:
01 let car1 = new Promise((_, reject) =>
02 setTimeout(reject, 2000, "Car 1 crashed in"));
03 let car2 = new Promise(resolve =>
04 setTimeout(resolve, 1500, "Car 2 completed"));
05 let car3 = new Promise(resolve =>
06 setTimeout(resolve, 3000, "Car 3 completed"));
07
08 Promise.race([car1, car2, car3])
09 .then(value => {
10 let result = '$(value) the race.';
11 })
12 .catch(err => {
13 console.log("Race is cancelled.", err);
14 });
What is the value of result when Promise.race executes?

A.Car 2 completed the race.
B.Car 3 completed the race.
C.Race is cancelled.
D.Car 1 crashed in the race.

Question 74

A developer needs to debug a Node.js web server because a runtime error keeps occurring at one of the endpoints.
The developer wants to test the endpoint on a local machine and make the request against a local server to look at the behavior. In the source code, the server.js file will start the server. The developer wants to debug the Node.js server only using the terminal.
Which command can the developer use to open the CLI debugger in their current terminal window?
(With corrected typing errors: node_inspect → node inspect, node_start_inspect → node start inspect.)

A.node start inspect server.js
B.node inspect server.js
C.node server.js --inspect
D.node -i server.js

Question 75

Given the JavaScript below:

Which code should replace the placeholder comment on line 05 to highlight accounts that match the search string'

A.'yellow : 'none'
B.'yellow' : null
C.'none1 : "yellow'
D.null : 'yellow'

Question 71

Question 72

Question 73

Question 74

Question 75

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