Salesforce Updated JavaScript-Developer-I Exam Questions and Answers by digby

getAttribute( ' value ' ) This returns the initial HTML attribute , not the live, updated value. Even if the user edits the text, the value attribute remains " Hello " because HTML attributes do not update dynamically.

Input elements have a property value that always reflects the live current text inside the field. So:

input.value

returns the user-entered value.

Therefore, line 04 must use the property, not the attribute:

console.log(input.value);

This ensures the updated input value is displayed.

JavaScript knowledge references (text-only)

HTML attributes are static and retrieved using getAttribute().

DOM element properties (like value) represent the current live state.

Input value changes update the .value property, not the attribute.

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From earlier pattern (cars/cats race):

One promise resolves the fastest with " Car 2 completed " (or analogous " Cat 2 completes " ).

Promise.race resolves with the first settled promise’s value.

In .then, value is " Car 2 completed " and:

let result = `${value} the race.`;

// " Car 2 completed the race. "

Thus result is " Car 2 completed the race. " → option A.

Animal class:

Has a constructor that sets this.name.

Has a makeSound method that logs a message using this.name.

Dog class:

Extends Animal.

Its constructor calls super(name) to run the parent constructor, which sets this.name.

It overrides makeSound() to log:

console.log(`${this.name} is barking.`);

Instantiation:

let myDog = new Dog( ' Puppy ' );

myDog.makeSound();

new Dog( ' Puppy ' ):

Calls Dog constructor with name = ' Puppy ' .

Inside, super(name) sets this.name = ' Puppy ' in the Animal constructor.

Then this.name = name; in the Dog constructor keeps it as ' Puppy ' .

myDog.makeSound():

Calls the overridden makeSound() in Dog.

Logs: " Puppy is barking. "

No reference errors, no undefined; the output is:

Puppy is barking.

Study Guide Concepts:

ES6 classes and inheritance (extends)

super() in subclass constructors

Method overriding in subclasses

Template literals: `${this.name} ...`

When execution hits the debugger; statement on line 06, JavaScript execution pauses at that point. Most modern browsers (for example, using DevTools) allow you to inspect the current scope , DOM, and various browser APIs in the console.

Let’s look at what is available precisely at line 06.

Current code state at the breakpoint:

Lines 01–04 define the Car constructor function.

Line 05 executes:

let carSpeed = document.getElementById( ' carSpeed ' );

So at line 06:

carSpeed is a variable containing a reference to a DOM element (the element with id " carSpeed " ).

Line 07 has not executed yet:

let fourWheels = new Car(carSpeed.value, ' red ' );

So fourWheels has not been created and is not accessible yet (it is in the temporal dead zone for the let declaration).

Now check each option:

Option A:

" A variable displaying the number of instances created for the Car object "

This code does not implement any mechanism to count instances of Car.

There is no static property, global counter, or similar variable tracking the number of Car instances.

At line 06, no instance of Car has even been created yet (new Car(...) is on line 07, which has not run).

Therefore, there is no such variable by default in JavaScript or DevTools.

This option is not available.

Option B:

" The information stored in the window.localStorage property "

At a breakpoint, the console is fully usable to inspect global objects.

window.localStorage is always accessible from the console (assuming standard browser context).

You can type:

window.localStorage

and inspect key/value pairs stored there.

This is independent of the current function or breakpoint line; localStorage is part of the Web Storage API on the window object.

So this information is indeed available in the console at line 06.

Option C:

" The values of the carSpeed and fourWheels variables "

At line 06:

carSpeed has been declared and assigned (line 05), so it is available, and its value (a DOM element) can be inspected.

fourWheels is declared on line 07 with let and has not yet been executed.

Variables declared with let and const are in a temporal dead zone before their declaration line completes.

At line 06, fourWheels is not yet initialized, and attempting to access it would result in a ReferenceError.

Thus, you can inspect carSpeed but not fourWheels. The option explicitly says " the values of the carSpeed and fourWheels variables " , which is not correct at this breakpoint, because fourWheels is not available yet.

Option D:

" The style, event listeners and other attributes applied to the carSpeed DOM element "

carSpeed holds a reference to a DOM element (document.getElementById( ' carSpeed ' )).

In DevTools, you can inspect this element in several ways:

Typing carSpeed in the console.

Inspecting it in the Elements panel.

From the console or Elements panel, you can view:

Its style (inline styles and computed styles).

Event listeners attached to it (using event listener viewer in DevTools).

Other attributes (id, class, etc.).

All of this is accessible at the point where execution is paused.

Therefore, this information is available at the breakpoint.

Conclusion:

B is available (global window.localStorage).

D is available (full inspection of the carSpeed DOM element).

A is not present in this code or environment.

C is partially wrong (only carSpeed exists; fourWheels does not yet).

So the two correct answers are:

Answer: B, D

References of JavaScript knowledge documents or Study Guide (concept names only):

debugger statement and pausing execution

JavaScript execution context and scope at a breakpoint

let declarations and temporal dead zone

Browser DevTools console and inspection of variables

DOM access via document.getElementById and inspection of elements

Web Storage API: window.localStorage