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| Section | Weight | Objectives |
|---|---|---|
| Topic 1: Debugging and Error Handling | 7% | - Console usage, breakpoints and debugging techniques - Error types and handling strategies |
| Topic 2: Variables, Types, and Collections | 23% | - JSON parsing and manipulation - Strings, numbers, dates, arrays and methods - Data types, type coercion, truthy/falsy values - Variable declaration and scope |
| Topic 3: Server Side JavaScript | 8% | - Node.js fundamentals and core modules - Package management and CLI tools |
| Topic 4: Browser and Events | 17% | - Browser APIs and developer tools - DOM selection and manipulation - Event handling, propagation, listeners |
| Topic 5: Asynchronous Programming | 13% | - Callbacks, promises, async/await - Event loop and execution flow |
| Topic 6: Objects, Functions, and Classes | 25% | - Function types, scope, closures, arrow functions - Object creation, properties, prototypes - ES6 classes, inheritance, modules, decorators |
| Topic 7: Testing | 7% | - Test coverage and improvement - Unit test structure and effectiveness |
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NEW QUESTION # 137
Refer to the code below:
01 funetion Person() (
02 thie. fixsttane = "Zoha'y
os}
05 Perscn.prototype = [
06 jek: x => 'Developer'
onde
09 const myFather = new Peracn():
10 const result = myFather.firstiame + ' * + myFather.jeb()
What is the value of result after line 10 executes?
Answer: C
NEW QUESTION # 138
Refer to the code below:
01 async function functionUnderTest(isOK) {
02 if (isOK) return 'OK';
03 throw new Error('not OK');
04 }
Which assertion accurately tests the above code?
Answer: D
Explanation:
The function:
async function functionUnderTest(isOK) {
if (isOK) return 'OK';
throw new Error('not OK');
}
Behavior:
If isOK is true:
The function resolves (fulfills the promise) with value 'OK'.
If isOK is false:
The function throws, which in an async function becomes a rejected promise with Error('not OK').
We want an assertion that accurately tests the successful path for isOK === true.
Key points about console.assert:
Signature: console.assert(condition, message?)
If condition is falsy, it logs message as an assertion failure.
If condition is truthy, nothing is logged.
We also must understand await:
await functionUnderTest(true) will resolve to the string 'OK'.
Now evaluate options.
Option A:
console.assert(await functionUnderTest(true), 'OK');
await functionUnderTest(true) → 'OK' (truthy).
console.assert('OK', 'OK');
Condition is 'OK' (truthy), so assertion passes.
The message 'OK' is only shown if the condition is falsy, which it is not.
This correctly verifies that the promise resolved (i.e., did not reject). Among the given options, this is the only one that both:
Uses await properly on the async function, and
Associates the message with the expected success "OK".
Option B:
console.assert(await (functionUnderTest(true), 'not OK'));
Inside the parentheses, the comma operator (a, b) evaluates a, discards it, and returns b.
So (functionUnderTest(true), 'not OK'):
Calls functionUnderTest(true) (returns a promise, but its result is discarded), The expression evaluates to the string 'not OK'.
Then await 'not OK' just resolves to 'not OK' immediately (not a promise).
console.assert('not OK');
Condition is 'not OK' (truthy), so the assertion passes regardless of what functionUnderTest actually does.
This does not meaningfully test the function and is misleading.
Option C:
console.assert(functionUnderTest(true), 'OK');
functionUnderTest(true) returns a Promise, not the string 'OK' directly.
A Promise object is always truthy.
So console.assert(promise, 'OK') will pass, even if the promise later rejects.
Also, there is no await, so we are not actually waiting for the async result.
This is not a correct way to assert on an async function's resolved value.
Option D:
console.assert(await functionUnderTest(true), 'not OK');
await functionUnderTest(true) still resolves to 'OK' (truthy).
console.assert('OK', 'not OK'); passes.
However, the message 'not OK' is the opposite of what we expect for the success case and is only used when the condition fails.
This makes the assertion logically inconsistent with the function behavior (it would show "not OK" if the assertion failed).
Therefore, the only assertion that:
Properly waits on the async function, and
Has expectation text that matches the successful behavior ('OK')
is:
Answe r: A
Study Guide / Concept Reference (no links):
async and await behavior in JavaScript
Promises resolving vs rejecting in async functions
console.assert(condition, message) usage
Truthy and falsy values in JavaScript
Comma operator (a, b) semantics
NEW QUESTION # 139
Refer to the code below:
01 function changeValue(param) {
02 param = 5;
03 }
04 let a = 10;
05 let b = a;
06
07 changeValue(b);
08 const result = a + ' - ' + b;
What is the value of result when the code executes?
Answer: D
Explanation:
Comprehensive and Detailed Explanation From Exact Extract JavaScript Knowledge:
We must understand pass-by-value for primitives in JavaScript.
Initial values:
let a = 10;
let b = a; // b gets a copy of the value 10
So:
a is 10
b is 10 (independent copy)
Function call:
changeValue(b);
Function definition:
function changeValue(param) {
param = 5;
}
param receives the value of b, which is 10.
Inside the function, param is a local variable.
param = 5; changes only this local copy.
It does not affect b outside the function.
After the function call:
a is still 10.
b is still 10.
Result:
const result = a + ' - ' + b;
a is 10.
b is 10.
String concatenation: '10 - 10'.
So result is:
"10 - 10"
Therefore, the correct option is:
Study Guide Concepts:
Primitive values (numbers, strings, booleans) are passed by value
Function parameters as local variables
String concatenation with +
Difference between mutating references vs primitives
________________________________________
NEW QUESTION # 140
Which statement parses successfully?
Answer: B
NEW QUESTION # 141
The developer has a function that prints "Hello" to an input name. To test this,thedeveloper created a function that returns "World". However the following snippet does not print " Hello World".
What can the developer do to change the code to print "Hello World" ?
Answer: A
NEW QUESTION # 142
......
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