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Salesforce JavaScript-Developer-I Exam Syllabus Topics:

Section	Weight	Objectives
Variables, Types, and Collections	23%	- Working with strings, numbers, dates, and booleans - Array methods and data manipulation - Truthy and falsy values - Variable declaration and initialization - Type coercion and conversion rules - JSON parsing and usage
Asynchronous Programming	13%	- Callbacks and callback hell - Fetch API and HTTP requests - Promises and chaining - Async/await syntax - Event loop and micro/macro tasks
Testing	7%	- Unit testing concepts - Test doubles and mocks - Code coverage and best practices - Testing frameworks and assertions
Debugging and Error Handling	7%	- Error types and exception handling - Defensive programming practices - Console methods and logging - Debugging tools and breakpoints
Objects, Functions, and Classes	25%	- Class syntax, inheritance, and prototypes - Decorators and advanced function patterns - Modules and imports/exports - Closures and execution context - Object creation, properties, and methods - Function definitions, parameters, and scope
Browsers and Events	17%	- Window and document object properties - Event handling, propagation, and delegation - Script loading and execution order - Browser APIs and Web Storage - Document Object Model (DOM) manipulation
Server-Side JavaScript	8%	- Core Node.js modules - Node.js fundamentals and runtime - Command-line tools and scripts - Module system and require/import

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Salesforce Certified JavaScript Developer (JS-Dev-101) Sample Questions (Q40-Q45):

NEW QUESTION # 40
Refer to the following object:
const cat ={
firstName: 'Fancy',
lastName: ' Whiskers',
Get fullName() {
return this.firstName + ' ' + this.lastName;
}
};
How can a developer access the fullName property for cat?

A. cat.function.fullName()
B. cat.fullName
C. cat.fullName()
D. cat.get.fullName

Answer: B

NEW QUESTION # 41
is below:
<input type="file" onchange="previewFile()">
<img src="" height="200" alt="Image Preview..."/>
The JavaScript portion is:
01 function previewFile(){
02 const preview = document.querySelector('img');
03 const file = document.querySelector('input[type=file]').files[0];
04 //line 4 code
05 reader.addEventListener("load", () => {
06 preview.src = reader.result;
07 },false);
08 //line 8 code
09 }
In lines 04 and 08, which code allows the user to select an image from their local
computer , and to display the image in the browser?

A. 04 const reader = new File();
08 if (file) URL.createObjectURL(file);
B. 04 const reader = new FileReader();
08 if (file) URL.createObjectURL(file);
C. 04 const reader = new File();
08 if (file) reader.readAsDataURL(file);
D. 04 const reader = new FileReader();
08 if (file) reader.readAsDataURL(file);

Answer: D

NEW QUESTION # 42
Considering type coercion, what does the following expression evaluate to?
true + ' 13 ' + NaN

A. ' 113NaN '
B. ' true13 '
C. 0
D. ' true13NaN '

Answer: D

Explanation:
Expression:
true + ' 13 ' + NaN
The + operator is left-associative, so evaluation order:
* true + ' 13 '
* When one operand is a string, + performs string concatenation.
* true is converted to string ' true ' .
* ' true ' + ' 13 ' # ' true13 ' .
* Result from step 1 with NaN:
' true13 ' + NaN
* Again, one operand is a string, so concatenation.
* NaN is converted to string ' NaN ' .
* ' true13 ' + ' NaN ' # ' true13NaN ' .
Final value: ' true13NaN ' .
So A is correct.
Why others are wrong:
* B: ' 113NaN ' would require true to coerce to 1 first and no string to be present, which is not the case because ' 13 ' forces string concatenation.
* C: 14 would require pure numeric addition, which is not the case once a string is involved.
* D: ' true13 ' ignores the final + NaN part.
Concepts: type coercion with +, boolean to string, NaN to string, left-associative evaluation.

NEW QUESTION # 43
A developer is setting up a new Node.js server with a client library that is built using events and callbacks.
The library:
* Will establish a web socket connection and handle receipt of messages to the server
* Will be imported with require, and made available with a variable called we.
The developer also wants to add error logging if a connection fails.
Given this info, which code segment shows the correct way to set up a client with two events that listen at execution time?

A. ws.connect (( ) => {
console.log('connected to client'); }).catch((error) => { console.log('ERROR' , error); }};
B. try{
ws.connect (( ) => {
console.log('connected to client'); });
} catch(error) { console.log('ERROR' , error); };
}
C. ws.on ('connect', ( ) => {
console.log('connected to client'); ws.on('error', (error) => { console.log('ERROR' , error); });
});
D. ws.on ('connect', ( ) => { console.log('connected to client'); }}; ws.on('error', (error) => { console.log('ERROR' , error); }};

Answer: D

NEW QUESTION # 44
A developer wants to create an object from a function in the browser using the code
below:
Function Monster() { this.name = 'hello' };
Const z = Monster();
What happens due to lack of the new keyword on line 02?

A. The z variable is assigned the correct object.
B. Window.name is assigned to 'hello' and the variable z remains undefined.
C. The z variable is assigned the correct object but this.name remains undefined.
D. Window.m is assigned the correct object.

Answer: B

NEW QUESTION # 45
......

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