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| Section | Weight | Objectives |
|---|---|---|
| Browser and Events | 17% | - DOM manipulation - Browser Developer Tools - Event handling, propagation, bubbling, and capturing |
| Server Side JavaScript | 8% | - Modules and file operations - Salesforce API integration - Node.js applications |
| Asynchronous Programming | 13% | - Event loop and asynchronous code execution - Callback patterns - Promises and async/await |
| Objects, Functions, and Classes | 25% | - Function declarations, expressions, and arrow functions - JavaScript modules (export, import) - Higher-order functions and closures - Object creation, properties, and prototypal inheritance - ES6 Classes, constructors, methods, and inheritance |
| Testing | 7% | - Unit testing with Jest - Automated testing strategies - Test-driven development principles |
| Variables, Types, and Collections | 23% | - Type coercion and type conversion - Variable declaration (var, let, const, scoping, hoisting) - JSON parsing and stringification - String manipulation and Date objects - Array manipulation (map, filter, reduce, forEach, find) |
| Debugging and Error Handling | 7% | - Logging strategies and debugging techniques - try-catch blocks |
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NEW QUESTION # 61
A developer implements a function that adds a few values.
function sum(num1, num2, num3) {
if (num3 === undefined) {
num3 = 0;
}
return num1 + num2 + num3;
}
Which three options can the developer invoke for this function to get a return value of 10?
Answer: A,C,D
Explanation:
The verified corrected answers are C, D, and E.
This function is a normal function, not a curried function:
function sum(num1, num2, num3) {
if (num3 === undefined) {
num3 = 0;
}
return num1 + num2 + num3;
}
It expects values to be passed in the same function call:
sum(num1, num2, num3);
Now check the valid corrected options.
Option C:
sum(5, 5, 0);
Calculation:
5 + 5 + 0
Result:
10
So C is correct.
Option D:
sum(10, 0);
Here, num3 is not provided, so it is undefined.
The function checks:
if (num3 === undefined) {
num3 = 0;
}
So the calculation becomes:
10 + 0 + 0
Result:
10
So D is correct.
Option E:
sum(5, 2, 3);
Calculation:
5 + 2 + 3
Result:
10
So E is correct.
Why A and B are incorrect as originally written:
sum(5)(5);
This calls sum(5) first. Since num2 is missing, the result becomes NaN. Then JavaScript tries to call that returned value as a function, which causes a TypeError.
sum()(10);
This also calls sum() first, producing NaN, and then attempts to call NaN as a function.
Those styles would only work if sum were written as a curried function, but the given implementation is not curried.
Therefore, the verified corrected answers are C, D, and E.
NEW QUESTION # 62
Original code:
01 let requestPromise = client.getRequest;
03 requestPromise().then((response) => {
04 handleResponse(response);
05 });
The developer wants to gracefully handle errors from a Promise-based GET request.
Which code modification is correct?
Answer: B
Explanation:
________________________________________
Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge Key JavaScript Promise rule:
try...catch does not catch asynchronous errors that occur in Promise chains.
Therefore, the correct way to handle errors in a Promise is:
promise.then(...).catch(...);
Analysis of options:
A and B:
Both wrap asynchronous code in try...catch, which does not catch Promise rejections.
try...catch only catches errors thrown synchronously inside the block.
C:
Correct. A .catch() on the Promise chain handles any error from the Promise returned by requestPromise().
D:
.finally() executes regardless of success or failure, but it does not receive the error object, so it cannot handle the error.
Thus the only valid solution is option C.
________________________________________
JavaScript Knowledge Reference (text-only)
Promise rejections must be handled with .catch().
try...catch only handles synchronous code.
.finally() does not receive a rejection reason.
NEW QUESTION # 63
A developer has 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 nor 5.
Which two test cases properly test scenarios for the fizzbuzz function?
Answer: C,D
Explanation:
The correct answers are B and D.
A strong test case checks whether the actual output matches the expected behavior of the function.
For Option B:
let res = fizzbuzz(15);
console.assert(res === 'fizzbuzz');
The number 15 is divisible by both 3 and 5:
15 % 3 === 0
15 % 5 === 0
So the correct return value is:
'fizzbuzz'
That makes option B a valid test.
For Option D:
let res = fizzbuzz(Infinity);
console.assert(res === '');
Infinity is not a normal finite divisible number. In JavaScript:
Infinity % 3
Infinity % 5
produce NaN, and comparisons such as:
Infinity % 3 === 0
are false.
So a typical fizzbuzz implementation would not treat Infinity as divisible by 3 or 5, meaning it should return:
''
That makes option D a valid test for the "neither divisible by 3 nor 5" path.
Now compare the incorrect options:
Option A is wrong because:
fizzbuzz(3)
should return:
'fizz'
not:
'buzz'
Option C is wrong because the function specification says the function returns strings such as 'fizz', 'buzz', 'fizzbuzz', or ''. It does not say the function returns numeric NaN.
So this assertion is not appropriate:
console.assert(isNaN(res));
Therefore, the verified answers are B and D.
NEW QUESTION # 64
Given the following code:
What is the output of line 02?
Answer: A
NEW QUESTION # 65
A developer is trying to convince management that their team will benefit from using Node.js for a backend server that they are going to create. The server will be a web server that handles API requests from a website that the team has already built using HTML, CSS, and JavaScript.
Which three benefits of Node.js can the developer use to persuade their manager?
Choose 3 answers
Answer: A,D,E
NEW QUESTION # 66
......
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