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NEW QUESTION # 69
Universal Container(UC) just launched a new landing page, but users complain that the website is slow. A developer found some functions that cause this problem.To verify this, the developer decides to do everything and log the time each of these three suspicious functions consumes.
console.time('Performance');
maybeAHeavyFunction();
thisCouldTakeTooLong();
orMaybeThisOne();
console.endTime('Performance');
Which function can the developer use to obtain the time spent by every one of the three functions?
Answer: D
NEW QUESTION # 70
A developer is leading the creation of a new web server for their team that will fulfill API requests from an existing client.
The team wants a web server that runs on Node.Js, and they want to use the new web framework Minimalist.Js. The lead developer wants to advocate for a more seasoned back-end framework that already has a community around it.
Which two frameworks could the lead developer advocate for?
Choose 2 answers
Answer: C,D
NEW QUESTION # 71
Given the expressionsvar1 and var2, what are two valid ways to return the concatenation of the two expressions and ensure it is string? Choose 2 answers
Answer: B,D
NEW QUESTION # 72
A developer is asked to fix some bugs reported by users. To do that, the developer adds a breakpoint for debugging.
01 function Car(maxSpeed, color) {
02 this.maxSpeed = maxSpeed;
03 this.color = color;
04 }
05 let carSpeed = document.getElementById('carSpeed');
06 debugger;
07 let fourWheels = new Car(carSpeed.value, 'red');
When the code execution stops at the breakpoint on line 06, which two types of information are available in the browser console?
Answer: B,C
Explanation:
Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:
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:
Reference 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
NEW QUESTION # 73
A developer creates a class that represents a news story based on the requirements that a Story should have a body, author, and view count. The code is shown below:
01 class Story {
02 // Insert code here
03 this.body = body;
04 this.author = author;
05 this.viewCount = viewCount;
06 }
07 }
Which statement should be inserted in the placeholder on line 02 to allow for a variable to be set to a new instance of a Story with the three attributes correctly populated?
Answer: D
Explanation:
Comprehensive and Detailed Explanation From Exact Extract JavaScript knowledge:
In ES6 class syntax, the special method used to initialize a new instance is called constructor.
A class definition syntax:
class ClassName {
constructor(param1, param2) {
this.prop1 = param1;
this.prop2 = param2;
}
}
The constructor method:
Is called automatically when you create a new instance with new ClassName(...).
Receives the arguments passed in the new expression.
Assigns values to this to set instance properties.
Applying this to Story
We want to be able to write:
const article = new Story('Some body', 'Author Name', 100);
and have:
article.body === 'Some body'
article.author === 'Author Name'
article.viewCount === 100
To achieve this, the class must have:
class Story {
constructor(body, author, viewCount) {
this.body = body;
this.author = author;
this.viewCount = viewCount;
}
}
So the correct line 02 is:
constructor(body, author, viewCount) {
Why the other options are incorrect
A . constructor() {
This defines a constructor with no parameters.
The lines inside the constructor use body, author, and viewCount, which would be undefined unless they exist in an outer scope (they normally do not).
This would lead to the instance properties being set to undefined in normal usage.
B . super(body, author, viewCount) {
super(...) is used inside a constructor of a subclass to call the parent class constructor.
You cannot use super(...) { as a method definition; this is invalid syntax in a class body.
Additionally, Story as given is not shown extending any class, so super is inappropriate here.
C . function Story(body, author, viewCount) {
Inside a class definition, you do not use the function keyword to define methods.
function Story(...) here would be invalid syntax in a class body.
Even if it were allowed, the special constructor method for a class is named constructor, not the class name.
Therefore, only:
constructor(body, author, viewCount) {
correctly declares the constructor for the Story class and ensures instances created with new Story(body, author, viewCount) have all three properties populated.
Reference / Study Guide concepts (no links):
ES6 class syntax
constructor method in classes
this and instance properties in classes
Difference between class constructors and regular functions
Invalid use of super and function inside class bodies
________________________________________
NEW QUESTION # 74
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