The Realest Study Materials JS-Dev-101 Dumps Updated Oct 19, 2026
LATEST JS-Dev-101 Exam Practice Material
Salesforce JS-Dev-101 Exam Syllabus Topics:
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NEW QUESTION # 50
Which option is true about the strict mode in imported modules?
- A. Imported modules are in strict mode whether you declare them as such or not.
- B. Add the statement use strict = false; before any other statements in the module to enable notstrict mode.
- C. Add the statement use non-strict; before any other statements in the module to enable notstrict mode.
- D. A developer can only reference notStrict() functions from the imported module.
Answer: A
Explanation:
Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:
In JavaScript, ES modules (files imported using import / export) have special semantics:
All code inside a module is automatically executed in strict mode.
This is specified by the ECMAScript standard and does not require the explicit "use strict"; directive.
Effects:
You do not need to write "use strict"; at the top of a module file.
You cannot turn strict mode off for module code.
All module top-level code is treated as strict.
Now evaluate each option:
Option A:
Add the statement use non-strict; before any other statements in the module to enable notstrict mode.
There is no use non-strict; directive in JavaScript.
The only directive recognized by engines is "use strict";.
You cannot explicitly enable a "non-strict" mode with such a string.
Option B:
Imported modules are in strict mode whether you declare them as such or not.
This matches the language specification.
ES modules are always in strict mode, automatically.
This is true.
Option C:
Add the statement use strict = false; before any other statements in the module to enable notstrict mode.
use strict = false; is not a directive; it is parsed as a normal expression, and does not affect strict mode.
There is no supported way to disable strict mode in modules.
Option D:
A developer can only reference notStrict() functions from the imported module.
There is no special notStrict() restriction in modules.
Functions exported/imported in modules are simply subject to strict mode rules like the rest of the module's code.
Therefore, the only correct statement is:
Study Guide / Concept Reference (no links):
ES modules (import / export)
Automatic strict mode in modules
"use strict"; directive for scripts vs modules
Inability to disable strict mode in ES module code
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NEW QUESTION # 51
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 thisnew requirement?
- A. deliveryDate.setDate( Date.current () + 9);
- B. deliveryDate.date = new Date(+9) ;
- C. deliveryDate.date = Date.current () + 9;
- D. deliveryDate.setDate(( new Date ( )).getDate () +9);
Answer: D
NEW QUESTION # 52
01 function changeValue(obj) {
02 obj.value = obj.value / 2;
03 }
04 const objA = {value: 10};
05 const objB = objA;
06
07 changeValue(objB);
08 const result = objA.value;
What is the value of result after the code executes?
- A. undefined
- B. low
- C. 0
- D. 1
Answer: D
Explanation:
objA is { value: 10 }.
objB = objA; → both variables reference the same object.
changeValue(objB);:
obj.value = obj.value / 2; // modifies the shared object
So:
objA.value becomes 10 / 2 = 5.
Thus result is 5.
________________________________________
NEW QUESTION # 53
Refer to the code below:
Which value can a developer expect when referencing country,capital,cityString?
- A. undefined
- B. An error
- C. 'NaN'
- D. 'London'
Answer: C
NEW QUESTION # 54
A developer is asked to fix some bugs reported by users. To do that, the developer adds abreakpoint for debugging.
Function Car (maxSpeed, color){
This.maxspeed =masSpeed;
This.color = color;
Let carSpeed = document.getElementById(' CarSpeed');
Debugger;
Let fourWheels =new Car (carSpeed.value, 'red');
When the code execution stops at the breakpoint on line 06, which two types of information are available in the browser console ?
Choose 2 answers:
- A. The values of the carSpeed and fourWheels variables
- B. A variable displaying the number of instances created for the Car Object.
- C. The style, event listeners and other attributes applied to the carSpeed DOM element
- D. The information stored in the window.localStorage property
Answer: C,D
NEW QUESTION # 55
Refer to the code below:
01 function changeValue(param) {
02 param = 5;
03 }
04 let a = 10;
05 let b = a;
06
07 changeValue(b);
08 const result = a + ' - ' + b;
What is the value of result when the code executes?
- A. 5-10
- B. 10-5
- C. 5-5
- D. 10-10
Answer: D
Explanation:
We must understand pass-by-value for primitives in JavaScript.
Initial values:
let a = 10;
let b = a; // b gets a copy of the value 10
So:
a is 10
b is 10 (independent copy)
Function call:
changeValue(b);
Function definition:
function changeValue(param) {
param = 5;
}
param receives the value of b, which is 10.
Inside the function, param is a local variable.
param = 5; changes only this local copy.
It does not affect b outside the function.
After the function call:
a is still 10.
b is still 10.
Result:
const result = a + ' - ' + b;
a is 10.
b is 10.
String concatenation: '10 - 10'.
So result is:
"10 - 10"
Therefore, the correct option is:
Study Guide Concepts:
Primitive values (numbers, strings, booleans) are passed by value
Function parameters as local variables
String concatenation with +
Difference between mutating references vs primitives
NEW QUESTION # 56
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.
Which code logs an error at boot time with an event?
- A. try {
server.start();
} catch(error) {
console.log('ERROR', error);
} - B. server.catch((error) => {
console.log('ERROR', error);
}); - C. server.on('error', (error) => {
console.log('ERROR', error);
}); - D. server.error((error) => {
console.log('ERROR', error);
});
Answer: C
Explanation:
Event-driven Node-style APIs expose events via .on(eventName, handler).
To listen for error events:
server.on('error', (error) => {
console.log('ERROR', error);
});
A and B assume methods .error or .catch that don't exist on typical event emitters.
C only catches synchronous errors from server.start(), not async event-based errors.
________________________________________
NEW QUESTION # 57
Refer to code below:
console.log(0);
setTimeout(() => (
console.log(1);
});
console.log(2);
setTimeout(() => {
console.log(3);
), 0);
console.log(4);
In which sequence will the numbers be logged?
- A. 02413
- B. 0
- C. 01234
- D. 02431
Answer: D
NEW QUESTION # 58
01 function Animal(size, type) {
02 this.type = type || 'Animal';
03 this.canTalk = false;
04 }
05
06 Animal.prototype.speak = function() {
07 if (this.canTalk) {
08 console.log("It spoke!");
09 }
10 };
11
12 let Pet = function(size, type, name, owner) {
13 Animal.call(this, size, type);
14 this.size = size;
15 this.name = name;
16 this.owner = owner;
17 }
18
19 Pet.prototype = Object.create(Animal.prototype);
20 let pet1 = new Pet();
Given the code above, which three properties are set for pet1?
- A. type
- B. canTalk
- C. owner
- D. speak
- E. name
Answer: A,B,E
Explanation:
When pet1 = new Pet(); is created:
Inside Pet constructor:
Animal.call(this, size, type);
this.size = size;
this.name = name;
this.owner = owner;
Animal.call(this, size, type):
Sets this.type = type || 'Animal' → 'Animal' (because type is undefined).
Sets this.canTalk = false.
Then this.size, this.name, this.owner are set (to undefined since no args passed), but they do exist as properties.
So as own properties, pet1 has: type, canTalk, size, name, owner.
speak is defined on Animal.prototype, so pet1.speak exists by inheritance, but is not an own data property created in the constructor.
From the listed options, three important properties directly set by constructor logic and clearly used in behavior are:
canTalk
name
type
Thus, C, D, E.
NEW QUESTION # 59
Refer to the code below:
const searchText = 'Yay! Salesforce is amazing!';
let result1 = searchText.search(/sales/i);
let result2 = searchText.search(/sales/);
console.log(result1);
console.log(result2);
After running this code, which result is displayed on the console?
- A. 5
0 - B. 5
-1 - C. true
false - D. 5
undefined
Answer: B
Explanation:
String: "Yay! Salesforce is amazing!"
Index positions:
'Y' at 0, 'a' at 1, 'y' at 2, '!' at 3, space at 4, 'S' at 5, 'a' at 6, 'l' at 7, 'e' at 8, 's' at 9, etc.
Substring "Sales" starts at index 5.
String.prototype.search with a regex returns the index of the first match or -1 if there is no match.
searchText.search(/sales/i);
/sales/i is case-insensitive because of the i flag.
It matches "Sales" beginning at index 5.
So result1 is 5.
searchText.search(/sales/);
/sales/ is case-sensitive.
It requires lowercase "sales".
The text has "Sales" with uppercase S, so this does not match.
search returns -1 when there is no match.
So result2 is -1.
Console output:
First log: 5
Second log: -1
Option D matches this.
Concepts: regex search, case sensitivity vs i flag, String.prototype.search return values.
NEW QUESTION # 60
Refer of the string below:
Const str = 'sa;esforce'=;
Which two statement result in the word 'Sale'?
Choose 2 answers
- A. str, substring(0,5) ;
- B. str, substr(1,5) ;
- C. str, substring(1,5) ;
- D. str, substr(0,5) ;
Answer: A,D
NEW QUESTION # 61
Which statement parses successfully?
- A. JSON.parse ("foo");
- B. JSON. parse (""foo"');
- C. JSON.parse ("foo");
- D. JSON.parse (""foo'");
Answer: B
NEW QUESTION # 62
A developer writes the code below to return a message to a user attempting to register a new username. If the username is available, a variable named nag is declared and assigned a value on line 03.
What is the value of msg when getAvailableabilityMessage ("newUserName") is executed and get Availability ("newUserName") returns true?
- A. undefined
- B. "msg is not defined"
- C. "newUserName"
- D. "User-name available"
Answer: D
NEW QUESTION # 63
Given the code below:
let numValue = 1982;
Which three code segments result in a correct conversion from number to string?
- A. let strValue = String(numValue);
- B. let strValue = '' + numValue;
- C. let strValue = numValue.toText();
- D. let strValue = (String)numValue;
- E. let strValue = numValue.toString();
Answer: A,B,E
Explanation:
Comprehensive and Detailed Explanation From JavaScript Knowledge:
We want to convert the number 1982 to a string.
Check each option:
A . numValue.toText()
There is no standard toText() method on numbers.
This will result in TypeError: numValue.toText is not a function.
B . String(numValue);
String() as a function converts its argument to a string.
String(1982) returns "1982".
This is correct.
C . '' + numValue;
'' is a string; + with a string operand performs string concatenation.
'' + 1982 → "1982".
This is a common shorthand for number-to-string conversion.
D . numValue.toString();
Number.prototype.toString() converts the number to its string representation.
1982..toString() or (1982).toString() returns "1982".
For the variable, numValue.toString() is valid: "1982".
E . (String)numValue;
This is not valid JavaScript casting syntax; it is more like a C/Java-style cast.
In JavaScript, that is parsed as a grouping expression (String) and then numValue; it does not convert numValue to a string.
Thus the correct answers are:
B . String(numValue);
C . '' + numValue;
D . numValue.toString();
Relevant concepts: primitive type conversion, String() casting, .toString(), coercion via + with strings.
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NEW QUESTION # 64
A developer has the function, shown below, that is called when a page loads.
Where can the developer see the log statement after loading the page in the browser?
- A. On the terminal console running the web server
- B. On the browser JavaScriptconsole
- C. On the webpage console log
- D. In the browser performance tools log
Answer: B
NEW QUESTION # 65
Refer to the code below:
01 const myFunction = arr => {
02 return arr.reduce((result, current) => {
03 return result + current;
04 }, 10);
05 }
What is the output of this function when called with an empty array?
- A. Throws an error
- B. Returns 0
- C. Returns NaN
- D. Returns 5 ← (Text here appears to be a typo; correct value is 10, see explanation.)
Answer: D
Explanation:
We call:
myFunction([]);
Inside:
arr.reduce((result, current) => {
return result + current;
}, 10);
Key points about Array.prototype.reduce:
Signature: array.reduce(callback, initialValue)
If initialValue is provided and the array is empty, reduce:
Does not call the callback at all.
Simply returns initialValue.
Here:
arr is [] (empty).
initialValue is 10.
So:
No iterations of the callback happen (no elements to process).
The return value is the initial value: 10.
So the actual output is:
myFunction([]) === 10;
Among the options:
A: 0 - incorrect, because the initial value is 10, not 0.
B: Throws an error - reduce throws only if the array is empty and there is no initialValue. Here we have an initial value, so no error.
C: NaN - there is no arithmetic with undefined or invalid values; we just return 10.
D: Returns 5 - the numeric value given is wrong; the correct value is 10.
Given the logic, the correct conceptual result is 10. The option text "Returns 5" is almost certainly a typo for "Returns 10". Since the letter that is intended to represent the correct behavior is D, we keep:
Answe r: D
Study Guide / Concept Reference (no links):
Array.prototype.reduce behavior with initialValue
Behavior of reduce on an empty array with and without initialValue
Return value when no iterations run
NEW QUESTION # 66
A developer is required to write a function that calculates the sum of elements in an array but is getting undefined every time the code is executed. The developer needs to find what is missing in the code below.
01 const sumFunction = arr => {
02 return arr.reduce((result, current) => {
03 //
04 result += current;
05 //
06 }, 10);
07 };
Which line replacement makes the code work as expected?
- A. 04 result = result + current;
- B. 05 return result;
- C. 03 if(arr.length == 0) { return 0; }
- D. 02 arr.map((result, current) => {
Answer: B
Explanation:
In a reduce callback, you must return the new accumulator value.
Currently:
(result, current) => {
result += current;
// no return
}
This returns undefined each time, so the accumulator becomes undefined on the next iteration, leading to incorrect results.
Fix by returning result:
const sumFunction = arr => {
return arr.reduce((result, current) => {
result += current;
return result; // line 05
}, 10);
};
Option D correctly adds the return.
Options A/B/C do not fix the missing return in the reducer and therefore do not resolve the core issue.
NEW QUESTION # 67
A developer has two ways to write a function:
Option A:
function Monster(){
this.growl = ()=>{
console.log('Grr!');
}
}
Option B:
function Monster(){};
Monster.prototype.growl = ()=>{
console.log('Grr!');
}
After deciding on an option, the developercreates 1000 monster objects.
How many growl methods are created with Option A and Option B?
- A. 1 for Option A, 1000 for Option B
- B. 1000 for both
- C. 1000 for Option A, 1 for Option B
- D. 1 methods for both
Answer: D
NEW QUESTION # 68
A class was written to represent items for purchase in an online store, and a second class representing items that are on sale at a discounted price. The constructor sets the name to the first value passed in. There is a new requirement for a developer to implement a description method that will return a brief description for Item and SaleItem.
01 let regItem = new Item('Scarf', 55);
02 let saleItem = new SaleItem('Shirt', 80, .1);
03 Item.prototype.description = function() { return 'This is a ' + this.name; }
04 console.log(regItem.description());
05 console.log(saleItem.description());
06
07 SaleItem.prototype.description = function() { return 'This is a discounted ' + this.name; } What is the output when executing the code above?
- A. This is a Scarf
This is a Shirt
This is a discounted Scarf
This is a discounted Shirt - B. This is a Scarf
Uncaught TypeError: saleItem.description is not a function
This is a Shirt
This is a discounted Shirt - C. This is a Scarf
Uncaught TypeError: saleItem.description is not a function
This is a Scarf
This is a discounted Shirt - D. This is a Scarf
This is a Shirt
This is a Scarf
This is a discounted Shirt
Answer: D
Explanation:
Comprehensive and Detailed
Assuming SaleItem inherits from Item via prototype (e.g. SaleItem.prototype = Object.create(Item.prototype)):
Lines 01-02: create regItem and saleItem.
Line 03: define Item.prototype.description.
Now both regItem and saleItem (via inheritance) have a description method from Item.prototype.
Line 04: regItem.description() → 'This is a Scarf'.
Line 05: saleItem.description() → 'This is a Shirt' (same method, but this.name is 'Shirt').
Line 07: SaleItem.prototype.description = ... overrides description only for SaleItem instances going forward.
If we imagine calling regItem.description() and saleItem.description() again after line 07:
regItem.description() still uses Item.prototype.description → 'This is a Scarf'.
saleItem.description() now uses SaleItem.prototype.description → 'This is a discounted Shirt'.
Those four lines correspond to option B.
________________________________________
NEW QUESTION # 69
A developer has an isDeg function that takes one argument, pts. They want to schedule the function to run every minute.
What is the correct syntax for scheduling this function?
- A. setTimeout(isDeg, 60000, 'cat');
- B. setTimeout(isDeg('cat'), 60000);
- C. setInterval(isDeg, 60000, 'cat');
- D. setInterval(isDeg('cat'), 60000);
Answer: C
Explanation:
setInterval(fn, delay, arg1, arg2, ...) calls fn every delay ms, passing extra arguments.
To call isDeg every 60 seconds with "cat":
setInterval(isDeg, 60000, 'cat');
Why others are wrong:
A/D: isDeg('cat') is called immediately, and its return value is scheduled, not the function.
C: setTimeout runs once after 60 seconds, not repeatedly.
NEW QUESTION # 70
......
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