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| Section | Weight | Objectives |
|---|---|---|
| Topic 1: Variables, Types, and Collections | 23% | - Array manipulation (map, filter, reduce, forEach, find) - Type coercion and type conversion - Variable declaration (var, let, const, scoping, hoisting) - String manipulation and Date objects - JSON parsing and stringification |
| Topic 2: Asynchronous Programming | 13% | - Callback patterns - Event loop and asynchronous code execution - Promises and async/await |
| Topic 3: Server Side JavaScript | 8% | - Node.js applications - Salesforce API integration - Modules and file operations |
| Topic 4: Browser and Events | 17% | - Event handling, propagation, bubbling, and capturing - Browser Developer Tools - DOM manipulation |
| Topic 5: Testing | 7% | - Test-driven development principles - Unit testing with Jest - Automated testing strategies |
| Topic 6: Objects, Functions, and Classes | 25% | - JavaScript modules (export, import) - ES6 Classes, constructors, methods, and inheritance - Higher-order functions and closures - Function declarations, expressions, and arrow functions - Object creation, properties, and prototypal inheritance |
| Topic 7: Debugging and Error Handling | 7% | - Logging strategies and debugging techniques - try-catch blocks |
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NEW QUESTION # 112
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 msg is declared and assigned a value on line 03.
function getAvailabilityMessage(item) {
if (getAvailability(item)) {
var msg = "Username available";
return msg;
}
}
Answer: A
Explanation:
The correct answer is C.
When getAvailability(item) returns true, the code inside the if block executes:
var msg = "Username available";
return msg;
The variable msg receives the string value:
"Username available"
Then that same value is returned from the function.
The key point is that var is function-scoped, not block-scoped. So msg belongs to the function scope of getAvailabilityMessage(). However, because the return msg; statement is inside the same if block, the function immediately returns the assigned string when the username is available.
Option A is incorrect because msg is defined before it is returned.
Option B is incorrect because "newUserName" is not assigned or returned anywhere in the function.
Option D would only happen if getAvailability(item) returned false, because then the function would finish without an explicit return value.
For the available username scenario, the verified answer is C.
NEW QUESTION # 113
A developer wants to create an object from a function in the browser using the code below.
What happens due to the lack of the mm keyword on line 02?
Answer: A
NEW QUESTION # 114
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?
Answer: A
NEW QUESTION # 115
Given the following code:
01 counter = 0;
02 const logCounter = () => {
03 console.log(counter);
04 };
05 logCounter();
06 setTimeout(logCounter, 2100);
07 setInterval(() => {
08 counter++;
09 logCounter();
10 }, 1000);
What will be the first four numbers logged?
Answer: D
Explanation:
We need to track the value of counter and the timing of each call to logCounter.
Initial state:
Line 01: counter = 0;
Line 02-04: logCounter logs the current value of counter.
Execution order and timing:
Line 05: logCounter();
Called immediately at time t = 0 ms.
counter is 0.
First log: 0.
Line 06: setTimeout(logCounter, 2100);
Schedules logCounter to run once after 2100 ms.
No log yet at this line.
Line 07-10: setInterval(() => { counter++; logCounter(); }, 1000);
Schedules a repeating callback every 1000 ms (1 second).
First interval callback runs at t ≈ 1000 ms.
Now follow the timeline:
t = 0 ms:
logCounter(); from line 05
Logs: 0
t = 1000 ms (first interval execution):
counter++; → counter goes from 0 to 1.
logCounter(); logs 1.
t = 2000 ms (second interval execution):
counter++; → counter goes from 1 to 2.
logCounter(); logs 2.
t = 2100 ms (timeout from line 06):
logCounter(); runs again.
counter is still 2 (next setInterval will be at t = 3000 ms).
Logs 2.
So the first four logs are:
0
1
2
2
Concatenated as in the options: 0122.
Therefore, the correct choice is:
Answe r: A
Study Guide / Concept Reference (no links):
setTimeout and setInterval timing behavior
Order of execution in the event loop
Closures capturing variables (here, logCounter using counter)
Understanding asynchronous scheduling in JavaScript
NEW QUESTION # 116
Given a value, which two options can a developer use to detect if the value is NaN?
Answer: C,D
Explanation:
We already know NaN is special: it is not equal to itself.
Check each:
A . value === Number.NaN
Number.NaN is NaN.
NaN === NaN is always false.
This will never be true; cannot reliably detect NaN.
B . value == NaN
NaN == NaN is also always false.
Again, this never detects NaN.
C . isNaN(value)
Global isNaN converts its argument to a number and then checks if the result is NaN.
This can detect NaN, but it may also return true for non-number values that coerce to NaN, such as isNaN('foo').
Regardless, it is a standard way to detect if a value is "NaN-like" in JavaScript.
D . Object.is(value, NaN)
Object.is(NaN, NaN) returns true.
This is a strict way to detect a value that is exactly NaN (no coercion).
Therefore, among the given choices, the two viable ways to detect NaN are:
isNaN(value)
Object.is(value, NaN)
NEW QUESTION # 117
......
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