Salesforce JS-Dev-101 Exam Dumps

Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:

We want mechanisms that persist data between page loads (i.e., after refresh or navigation), in the browser.

A . localStorage

Part of the Web Storage API.

Data persists across page reloads and browser restarts (until explicitly cleared).

Scoped per origin (protocol + host + port).

This is a correct persistent storage API.

B . indexedDB

A low-level, client-side NoSQL database in the browser.

Stores large amounts of structured data and persists across reloads and sessions.

This is also a correct persistent API.

C . cookies

Small key/value pairs stored by the browser and often sent with HTTP requests.

Can have expiration dates and persist across page loads and sessions.

They are a traditional persistence mechanism in browsers.

So cookies also qualify.

D . global variables

Global JS variables exist only for the life of the current page context.

When the page is refreshed or navigated away, they are lost.

They do not persist between page loads.

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Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

When async is added to a function:

async function example() {}

JavaScript guarantees:

The function always returns a Promise, regardless of what is returned inside.

Inside the function, await pauses execution until a Promise resolves.

Code appears synchronous even though it uses asynchronous behavior.

Analysis of each option:

A incorrect:

Not 'sometimes'---an async function always returns a Promise.

B incorrect:

Async functions can be called just like normal functions.

C incorrect:

Async/await has nothing to do with classes specifically.

D correct:

This is the standard description:

''Async functions behave asynchronously but allow writing code that looks synchronous.''

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JavaScript Knowledge Reference (text-only)

async functions always return Promises.

await pauses execution of the async function.

Async/await syntax creates synchronous-looking code on top of asynchronous operations.

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Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

Node.js event-based modules use the EventEmitter pattern.

The correct syntax for listening to events is:

emitter.on('eventName', callback)

The server library emits an 'error' event, which must be listened to using .on.

Option analysis:

A: .catch is for Promises, not EventEmitters.

B: .error is not an EventEmitter method.

C: Correct. Listens to the 'error' event.

D: try...catch only captures synchronous errors, not event-based asynchronous errors.

Therefore, the correct answer is option C.

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JavaScript Knowledge Reference (text-only)

The EventEmitter API uses on(event, handler) to listen for events.

Errors emitted asynchronously cannot be caught with try...catch.

The 'error' event is standard for Node.js modules to signal operational errors.

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Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge

Initial array:

[1, 2, 3, 4, 4, 5, 4, 4]

The loop removes every value equal to 4:

array.splice(i, 1) removes the element at index i and shifts all later elements left.

i-- ensures the next index is checked correctly after the shift, preventing skipping elements.

Step-by-step removal:

Remove the first 4 array becomes [1,2,3,4,5,4,4]

Remove next 4 [1,2,3,5,4,4]

Remove next 4 [1,2,3,5,4]

Remove last 4 [1,2,3,5]

Final result:

[1,2,3,5]

Option B is correct.

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JavaScript Knowledge Reference (text-only)

splice(index, deleteCount) removes elements and shifts remaining items.

Adjusting the loop index when deleting prevents skipping items.

Arrays update length dynamically after splice().