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| Section | Weight | Objectives |
|---|---|---|
| Topic 1: Variables, Types, and Collections | 23% | - Strings, numbers, dates, arrays and methods - Data types, type coercion, truthy/falsy values - JSON parsing and manipulation - Variable declaration and scope |
| Topic 2: Objects, Functions, and Classes | 25% | - Function types, scope, closures, arrow functions - ES6 classes, inheritance, modules, decorators - Object creation, properties, prototypes |
| Topic 3: Testing | 7% | - Unit test structure and effectiveness - Test coverage and improvement |
| Topic 4: Browser and Events | 17% | - DOM selection and manipulation - Event handling, propagation, listeners - Browser APIs and developer tools |
| Topic 5: Debugging and Error Handling | 7% | - Error types and handling strategies - Console usage, breakpoints and debugging techniques |
| Topic 6: Asynchronous Programming | 13% | - Event loop and execution flow - Callbacks, promises, async/await |
| Topic 7: Server Side JavaScript | 8% | - Node.js fundamentals and core modules - Package management and CLI tools |
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NEW QUESTION # 66
A team at Universal Containers works on a big project and uses Yarn to deal with the project's dependencies. A developer added a dependency to manipulate dates and pushed the updates to the remote repository. The rest of the team complains that the dependency does not get downloaded when they execute yarn.
What could be the reason for this?
Answer: A
Explanation:
If the dependency was added as a dev dependency (yarn add --dev), it goes into devDependencies.
When NODE_ENV=production, Yarn (and npm) typically skip devDependencies on install.
Thus the package doesn't get installed for other team members in a production environment.
YARN_ENV is not a standard variable, --save is npm syntax (and Yarn saves by default), and --add is not how Yarn works (the command itself is yarn add).
NEW QUESTION # 67
Which statement allows a developer to update the browser navigation history without a page refresh?
Answer: C
Explanation:
The correct answer is C.
The browser provides the History API through:
window.history
To add a new entry to the browser's session history without refreshing the page, JavaScript uses:
window.history.pushState(state, title, url);
So the valid statement is:
window.history.pushState(newStateObject, '', null);
This updates the browser history stack without forcing a full page reload. It is commonly used in single-page applications when changing views or routes dynamically.
The method accepts three arguments:
window.history.pushState(stateObject, title, url);
stateObject stores custom data associated with the history entry.
title is usually passed as an empty string because many browsers ignore it.
url optionally changes the displayed URL. Passing null means no new URL is provided.
Option A is incorrect because:
window.customHistory
is not the standard browser History API object.
Option B is incorrect because:
createState()
is not a valid History API method.
Option D is incorrect because:
updateState()
is not a valid History API method.
The correct browser API method is:
window.history.pushState()
Therefore, the verified answer is C.
NEW QUESTION # 68
Given the code below:
01 const delay = async delay => {
02 return new Promise((resolve, reject) => {
03 console.log(1);
04 setTimeout(resolve, delay);
05 });
06 };
07
08 const callDelay = async () => {
09 console.log(2);
10 const yup = await delay(1000);
11 console.log(3);
12 };
13
14 console.log(4);
15 callDelay();
16 console.log(5);
What is logged to the console?
Answer: A
Explanation:
Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge:
Execution order:
Top-level code runs synchronously:
Line 14: console.log(4); → logs 4.
Line 15: callDelay(); is called.
Inside callDelay:
Line 9: console.log(2); → logs 2.
Line 10: await delay(1000);:
Calls delay(1000).
Inside delay(1000):
Line 3: console.log(1); → logs 1.
Line 4: setTimeout(resolve, delay); schedules resolve in 1000 ms.
delay returns a pending Promise. await pauses callDelay here and returns control to the event loop.
Back to top-level:
Line 16: console.log(5); → logs 5.
So synchronous log sequence is: 4, 2, 1, 5.
After ~1000 ms:
The setTimeout in delay resolves the Promise.
The await in callDelay resumes.
Line 11: console.log(3); → logs 3.
Final log order: 4 2 1 5 3.
Both A and B show the same sequence; one must be chosen, so A is correct.
Concepts: async/await flow, Promise resolution timing, event loop, and ordering of synchronous vs timer callbacks.
________________________________________
NEW QUESTION # 69
Given the following code:
Counter = 0;
const logCounter = () => {
console.log(counter);
);
logCounter();
setTimeout(logCOunter, 1100);
setInterval(() => {
Counter++
logCounter();
}, 1000);
What is logged by the first four log statements?
Answer: D
NEW QUESTION # 70
Universal Containers (UC) just launched a new landing page, but users complain that the website is slow. A developer found some functions that might cause this problem. To verify this, the developer decides to execute everything and log the time each of these three suspicious functions consumes.
01 console.time('Performance');
02
03 maybeAHeavyFunction();
04
05 thisCouldTakeTooLong();
06
07 orMaybeThisOne();
08
09 console.endTime('Performance');
Which function can the developer use to obtain the time spent by every one of the three functions?
Answer: B
Explanation:
JavaScript consoles (browsers and Node) provide timing utilities:
console.time(label) - starts a timer with the given label.
console.timeEnd(label) - stops the timer and logs the total elapsed time.
console.timeLog(label) - logs the current elapsed time without stopping the timer.
To measure the time taken by each function separately while still using a single overall timer, you can log intermediate times:
console.time('Performance');
maybeAHeavyFunction();
console.timeLog('Performance', 'after maybeAHeavyFunction');
thisCouldTakeTooLong();
console.timeLog('Performance', 'after thisCouldTakeTooLong');
orMaybeThisOne();
console.timeLog('Performance', 'after orMaybeThisOne');
console.timeEnd('Performance');
Each console.timeLog('Performance') call prints the elapsed time since console.time('Performance') was started, so you can infer how long each function took.
Note: console.endTime in the original snippet is incorrect; the real method is console.timeEnd.
Why other options are incorrect:
B . console.trace()
Prints a stack trace, not timing information.
C . console.timeStamp()
Used with browser performance tools; it does not directly show elapsed times like timeLog or timeEnd.
D . console.getTime()
Not a standard console method.
Thus, the function that can be used to obtain timing between calls is:
Answe r: A
Study Guide Concepts:
console.time, console.timeLog, console.timeEnd
Measuring performance and intermediate timings
Standard console debugging API methods
NEW QUESTION # 71
......
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