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| Section | Weight | Objectives |
|---|---|---|
| Debugging and Error Handling | 7% | - Console usage, breakpoints and debugging techniques - Error types and handling strategies |
| Variables, Types, and Collections | 23% | - JSON parsing and manipulation - Strings, numbers, dates, arrays and methods - Variable declaration and scope - Data types, type coercion, truthy/falsy values |
| Objects, Functions, and Classes | 25% | - Object creation, properties, prototypes - ES6 classes, inheritance, modules, decorators - Function types, scope, closures, arrow functions |
| Server Side JavaScript | 8% | - Package management and CLI tools - Node.js fundamentals and core modules |
| Browser and Events | 17% | - DOM selection and manipulation - Event handling, propagation, listeners - Browser APIs and developer tools |
| Asynchronous Programming | 13% | - Event loop and execution flow - Callbacks, promises, async/await |
| Testing | 7% | - Test coverage and improvement - Unit test structure and effectiveness |
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NEW QUESTION # 120
Which actions can be done using the JavaScript browser console?
Answer: B,C,E
Explanation:
A: Yes. You can run arbitrary JS in the console (even if it doesn't touch the page).
B: Yes. You can inspect and modify DOM nodes via JS.
C: Performance reports are mainly in the Performance tab, not the console.
D: Yes. You can alter the DOM and redefine or override JS functions/variables at runtime.
E: You can read and set document.cookie, but HttpOnly "security cookies" cannot be read or changed from JS.
NEW QUESTION # 121
At Universal Containers, every team has its own way of copying JavaScript objects. The code snippet shows an implementation from one team:
01 function Person() {
02 this.firstName = "John";
03 this.lastName = "Doe";
04 this.name = () => {
05 console.log('Hello ${this.firstName} ${this.lastName}');
06 }
07 }
08
09 const john = new Person();
10 const dan = JSON.parse(JSON.stringify(john)); // (intended deep copy)
11 dan.firstName = 'Dan';
12 dan.name();
(Original line 10 is logically intended to be JSON.parse(JSON.stringify(john)) to perform a JSON clone.) What is the output of the code execution?
Answer: D
Explanation:
JSON.stringify(john) converts the john object into a JSON string.
When you JSON.parse that string back, you get a plain object:
Only data that can be represented in JSON is preserved (numbers, strings, booleans, arrays, plain objects).
Functions are not preserved and are dropped.
So dan is a plain object with properties firstName and lastName, but no name method.
Therefore, dan.name is undefined, and dan.name() throws:
TypeError: dan.name is not a function
The literal string interpolation inside console.log('Hello ${...}') is also wrong (single quotes), but the code never reaches that line.
NEW QUESTION # 122
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 โ node inspect, node_start_inspect โ node start inspect.)
Answer: B
Explanation:
Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:
Node.js includes a built-in command-line (CLI) debugger. To use it directly in the terminal, the standard command is:
node inspect server.js
This:
Starts server.js under the Node.js inspector.
Opens the CLI debugger right in the terminal window where you ran the command.
Lets you interactively:
Step through code
Set breakpoints
Inspect variables
Continue execution, etc.
Why B is correct:
Option B (corrected to node inspect server.js) is exactly the standard Node.js command to run a script under the CLI debugger in the current terminal.
It does not rely on any external GUI tools.
You stay entirely in the terminal to debug.
Why the other options are incorrect:
A . node start inspect server.js
There is no start subcommand like this in standard Node.js CLI.
This is not a valid Node.js debugging command.
C . node server.js --inspect
This starts Node.js with the Inspector protocol enabled and is typically used to connect external tools like Chrome DevTools or VS Code.
It does not open the CLI debugger in the current terminal. Instead, it opens a debugging port that other tools attach to.
The question specifically says "only using the terminal" and "open the CLI debugger in their current terminal window", which points to node inspect, not --inspect.
D . node -i server.js
-i starts Node in interactive REPL mode, optionally after running a script.
This is for an interactive shell, not the Node debugger.
It does not provide breakpoint/step/next/continue debugging features like the CLI debugger.
Therefore, the only option that opens the Node.js CLI debugger in the current terminal is:
JavaScript / Node.js knowledge / Study Guide references (concept names only, no links):
Node.js CLI debugger: node inspect <script>
Node.js inspector protocol: node --inspect
Difference between CLI debugger and DevTools-based debugging
Node.js command-line options and subcommands
________________________________________
NEW QUESTION # 123
Refer to the code below:
01 const server = require('server');
02 /* Insert code here */
A developer imports a library that creates a web server. Theimported library uses events and callbacks to start the servers Which code should be inserted at the line 03 to set up an event and start the web server ?
Answer: B
NEW QUESTION # 124
Which two code snippets show working examples of a recursive function?
Answer: C,D
Explanation:
return startNumber;
}
};
(Note: Option D is shown here with corrected syntax: lowercase return and matching parentheses.) Explanation:
A recursive function is a function that calls itself and has a base case to terminate the recursion.
Evaluate each option:
Option A:
const sumToTen = numVar => {
if (numVar < 0)
return;
return sumToTen(numVar + 1);
};
This function calls itself: sumToTen(numVar + 1) - so it is recursive.
However, the base condition is if (numVar < 0) return;.
If you call sumToTen(0):
numVar < 0 is false, so it calls sumToTen(1), then sumToTen(2), and so on, incrementing forever.
There is no condition to stop the recursion when numVar increases; it will eventually cause a stack overflow.
This code does not represent a properly working recursive function with a valid termination for increasing values and is not a good example of correct recursion.
Option B:
function factorial(numVar) {
if (numVar < 0) return;
if (numVar === 0) return 1;
return numVar - 1;
}
This function does not call itself anywhere.
It has conditional returns, but there is no recursive call such as factorial(numVar - 1).
Therefore, it is not recursive at all.
Option C:
const factorial = numVar => {
if (numVar < 0) return;
if (numVar === 0) return 1;
return numVar * factorial(numVar - 1);
};
This is a classic recursive factorial implementation.
It calls itself with a smaller argument: factorial(numVar - 1).
Base cases:
If numVar < 0, it simply returns (could be treated as invalid input).
If numVar === 0, it returns 1, which is the mathematical definition of 0! (zero factorial).
For positive integers, it correctly multiplies numVar by factorial(numVar - 1) until it reaches the base case.
This is a correct and working recursive function.
Option D (corrected):
let countingDown = function(startNumber) {
if (startNumber > 0) {
console.log(startNumber);
return countingDown(startNumber - 1);
} else {
return startNumber;
}
};
This function also calls itself: countingDown(startNumber - 1).
Base case:
When startNumber is not greater than 0 (i.e., 0 or negative), it returns startNumber and stops recursing.
For example, countingDown(3) would:
Log 3, call countingDown(2)
Log 2, call countingDown(1)
Log 1, call countingDown(0)
At 0, it hits the else branch and returns 0, ending the recursion.
This is a valid working recursive function structure (once syntax is corrected).
Therefore, the snippets that show working recursive functions are:
Answe r: C, D
Study Guide / Concept Reference (no links):
Definition of recursion: a function calling itself
Base case vs recursive step
Recursive factorial implementation
Recursive countdown example
Importance of a terminating condition to avoid infinite recursion
NEW QUESTION # 125
......
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