JavaScript-Developer-I Salesforce Certified JavaScript Developer (JS-Dev-101) Free Practice Exam Questions (2026 Updated)

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:

Answer: B

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

Object.preventExtensions(obj) This built-in JavaScript method marks an object so that no new properties can be added to it. Existing properties can still be read and updated, but adding new ones is disallowed.

const newObjBook = objBook; Both variables reference the same object in memory. JavaScript objects are assigned by reference, not copied.

newObjBook.author = " Robert " ; Because the object has been marked as non-extensible, JavaScript will not allow new properties to be added. The behavior depends on mode:

In non-strict mode: the assignment silently fails and does nothing.

In strict mode: this would throw a TypeError.

Since nothing indicates strict mode, this is non-strict behavior, making the assignment fail silently.

Therefore, the object remains:

{ title: " JavaScript " }

Both objBook and newObjBook point to the same unchanged object.

This matches option A.

JavaScript knowledge references (text-only)

Object.preventExtensions() prevents adding new properties.

Assigning an object to another variable copies the reference, not the object.

Adding a property to a non-extensible object silently fails in non-strict mode.

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Two key browser events:

DOMContentLoaded (fired on document): Fired when the HTML document has been completely loaded and parsed, without waiting for stylesheets, images, and subresources to finish loading.

load (fired on window): Fired when the entire page is fully loaded, including all dependent resources such as stylesheets and images.

The requirement states:

“… when the webpage is fully loaded with HTML content and all related files.”

That matches the semantics of the load event on the window object.

So the correct code is:

window.addEventListener( ' load ' , personalizeWebsiteContent);

Why others are incorrect:

A: DOMContentLoaded fires earlier, when HTML is parsed, but before all related files (images, some styles, etc.) are guaranteed to be loaded.

B: ' onDOMContentLoaded ' is not a valid event name; the event is ' DOMContentLoaded ' .

D: When using addEventListener, the event type is ' load ' , not ' onload ' . ' onload ' is the name of the handler property (window.onload = ...), not the event string.

Relevant concepts: window.load event, DOMContentLoaded, addEventListener syntax, page load lifecycle.