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| Section | Weight | Objectives |
|---|---|---|
| Variables, Types, and Collections | 23% | - Strings, numbers, dates, arrays and methods - Data types, type coercion, truthy/falsy values - Variable declaration and scope - JSON parsing and manipulation |
| Objects, Functions, and Classes | 25% | - ES6 classes, inheritance, modules, decorators - Object creation, properties, prototypes - Function types, scope, closures, arrow functions |
| Server Side JavaScript | 8% | - Node.js fundamentals and core modules - Package management and CLI tools |
| Browser and Events | 17% | - Browser APIs and developer tools - DOM selection and manipulation - Event handling, propagation, listeners |
| Asynchronous Programming | 13% | - Event loop and execution flow - Callbacks, promises, async/await |
| Testing | 7% | - Unit test structure and effectiveness - Test coverage and improvement |
| Debugging and Error Handling | 7% | - Error types and handling strategies - Console usage, breakpoints and debugging techniques |
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NEW QUESTION # 58
Refer to the code below:
01 new Promise((resolve, reject) => {
02 const fraction = Math.random();
03 if (fraction > 0.5) reject('fraction > 0.5, ' + fraction);
04 resolve(fraction);
05 })
06 .then(() => console.log('resolved'))
07 .catch((error) => console.error(error))
08 .finally(() => console.log('when am I called?'));
When does Promise.finally on line 08 get called?
Answer: B
Explanation:
Behavior of Promise.prototype.finally:
.finally(handler) registers a callback that runs when the promise is settled, meaning:
Either fulfilled (resolved), or
rejected.
Important points:
The finally callback does not receive the promise's value or error (unlike then and catch).
It is executed after the promise is settled, but before the resolution value or rejection reason is passed further down the chain.
It runs in both success and failure paths.
In the given code:
The promise may either:
Call reject('fraction > 0.5, ' + fraction) if fraction > 0.5, or
Call resolve(fraction) otherwise.
In both cases:
If it resolves, .then(() => console.log('resolved')) runs, and then .finally(...) is executed.
If it rejects, .catch((error) => console.error(error)) runs, and then .finally(...) is executed.
So .finally runs:
Not just "when rejected".
Not just "when resolved".
But whenever the promise is resolved or rejected.
Therefore, the correct choice is:
D . When resolved or rejected.
NEW QUESTION # 59
Refer tothe code below:
What is the value of result after line 10 executes?
Answer: B
NEW QUESTION # 60
Refer to the code below:
let o = {
get js() {
let city1 = String("st. Louis");
let city2 = String(" New York");
return {
firstCity: city1.toLowerCase(),
secondCity: city2.toLowerCase(),
}
}
}
What value can a developer expect when referencing o.js.secondCity?
Answer: B
NEW QUESTION # 61
Refer to the code below:
let productSKU = '8675309';
A developer has a requirement to generate SKU numbers that are always 19 characters long, starting with 'sku', and padded with zeros.
Which statement assigns the value sku000000008675309?
Answer: C
Explanation:
We start with:
let productSKU = '8675309';
The requirement:
Final SKU string:
Length: 19 characters.
Starts with 'sku'.
Remaining characters are digits padded with zeros on the left (to reach total length).
We can use String.prototype.padStart and String.prototype.padEnd:
str.padStart(targetLength, padString)
If str.length < targetLength, it adds padString to the start until the length is targetLength.
str.padEnd(targetLength, padString)
Similar, but adds padString to the end.
We want a pattern like:
First, pad the numeric part out to a fixed length with zeros.
Then, pad to total length with 'sku' at the start.
Analyze Option B
productSKU = productSKU.padStart(16, '0').padStart(19, 'sku');
Step 1: productSKU.padStart(16, '0')
Initial productSKU is '8675309' (length 7).
After padStart(16, '0'), we pad zeros on the left to reach length 16.
We need 16 − 7 = 9 zeros:
Result after step 1:
productSKU === '0000000008675309' // length 16
Step 2: .padStart(19, 'sku')
Now productSKU has length 16.
We call padStart(19, 'sku'):
We need 19 − 16 = 3 extra characters.
The pad string 'sku' is exactly 3 characters, so it is added as-is at the start.
Result after step 2:
productSKU === 'sku0000000008675309' // length 19
This satisfies:
Length 19.
Starts with 'sku'.
Remaining characters are zeros plus the original digits, i.e. a zero-padded numeric section.
While the literal sample sku000000008675309 in the text has a slightly different count of zeros, Option B follows the requirement pattern:
3 characters of 'sku'
Numeric part padded with zeros to make 16 characters total for the numeric part
3 + 16 = 19 total characters
Option B matches the intended logic using padStart and padEnd.
Why the other options are incorrect
Option A:
productSKU = productSKU.padEnd(16, '0').padStart('sku');
padEnd(16, '0') produces '8675309000000000' (original number followed by zeros).
padStart('sku') is invalid usage:
padStart takes a numeric target length as the first argument, not a string.
Passing 'sku' as the first argument leads to type coercion that does not achieve the intended behavior.
This will not reliably produce the desired SKU.
Option C:
productSKU = productSKU.padEnd(16, '0').padStart(19, 'sku');
First padEnd(16, '0') from '8675309' gives '8675309000000000' (length 16, zeros at the end).
Then padStart(19, 'sku') adds 3 chars 'sku' at the front:
Result: 'sku8675309000000000'.
This string starts with 'sku', but the zeros are at the end of the digits, not padding the numeric part on the left as desired.
Option D:
productSKU = productSKU.padStart(19, '0').padStart('sku');
First padStart(19, '0') pads zeros at the left to make the length 19.
Then padStart('sku') again incorrectly uses a string where a numeric targetLength is required.
This will not produce the correct SKU format.
Therefore, the only option that correctly uses padStart to create a 16-character zero-padded numeric portion and then a 19-character string starting with 'sku' is:
Answe r: B
Reference / Study Guide concepts (no links):
String.prototype.padStart(targetLength, padString)
String.prototype.padEnd(targetLength, padString)
String length calculations
Left-padding numeric strings with zeros
Building prefixed identifiers with fixed total length
NEW QUESTION # 62
Refer to the code below:
01 let sayHello = () => {
02 console.log('Hello, World!');
03 };
Which code executes sayHello once, two minutes from now?
Answer: D
Explanation:
To schedule a function for later execution in JavaScript, the standard built-in method is:
setTimeout(functionReference, delayInMilliseconds)
Characteristics of setTimeout():
Executes only once.
Delay is specified in milliseconds.
Requires passing the function reference, not calling the function.
Two minutes is:
2 minutes = 120 seconds = 120,000 milliseconds
Now evaluate each option:
Option A: delay(sayHello, 120000);
Incorrect.
There is no built-in delay() function in JavaScript.
Option B: setTimeout(sayHello, 120000);
Correct.
sayHello is passed as a function reference, so it will execute once after 120,000 ms.
Option C: setTimeout(sayHello(), 120000);
Incorrect.
sayHello() calls the function immediately, and the return value (undefined) is passed to setTimeout.
This executes the function right away instead of after two minutes.
Option D: setInterval(sayHello, 120000);
Incorrect.
setInterval() repeats execution every 120,000 ms.
The question requires executing the function once, so this cannot be correct.
JavaScript Knowledge Reference (text-only)
setTimeout() schedules a function to run once after a specified delay.
Passing functionName gives a reference; passing functionName() invokes it immediately.
setInterval() repeats indefinitely, unlike setTimeout().
NEW QUESTION # 63
......
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