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| Section | Weight | Objectives |
|---|---|---|
| Topic 1: Asynchronous Programming | 13% | - Promises (creation, chaining, error handling) - Callbacks - Asynchronous patterns for business requirements - Async/Await syntax - Event loop and execution flow |
| Topic 2: Server Side JavaScript | 8% | - Package management (npm) - CLI commands - Node.js fundamentals - Server-side JavaScript implementations - Core Node.js modules |
| Topic 3: Debugging and Error Handling | 7% | - Custom error types - Console methods for debugging - Error handling techniques (try/catch/finally) - Breakpoints and code inspection |
| Topic 4: Objects, Functions, and Classes | 25% | - Function declarations and expressions - Arrow functions - Execution flow and context - Prototypal inheritance - Higher-order functions - Variable scope and closures - Modules and decorators - Object creation and manipulation - ES6 classes and inheritance |
| Topic 5: Browser and Events | 17% | - Interacting with forms and user input - Event handling and listeners - Browser Developer Tools usage - Browser-specific APIs - DOM manipulation - Event propagation (bubbling and capturing) |
| Topic 6: Variables, Types, and Collections | 23% | - Truthy and falsy evaluations - JSON parsing and manipulation - Arrays and collections - Primitive and complex data types - Strings, numbers, and dates - Variable declarations and initialization - Type coercion and conversion |
| Topic 7: Testing | 7% | - Unit testing concepts - Test coverage and reliability - Test effectiveness evaluation - Writing and modifying unit tests |
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NEW QUESTION # 109
Refer to the code:
Given the code above, which three properties are set for pet1? Choose 3 answers
Answer: A,B,C
NEW QUESTION # 110
Which option is true about the strict mode in imported modules?
Answer: A
NEW QUESTION # 111
developer creates a new web server that uses Node.js. It imports a server library that uses events and callbacks for handling server functionality.
The server library is imported with require and is made available to the code by a variable named server. The developer wants to log any issues that the server has while booting up.
Given the code and the information the developer has, which code logs an error at boost with an event?
Answer: A
NEW QUESTION # 112
A developer implements and calls the following code when an application state change occurs:
Const onStateChange =innerPageState) => {
window.history.pushState(newPageState, ' ', null);
}
If the back button is clicked after this method is executed, what can a developer expect?
Answer: A
NEW QUESTION # 113
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: B
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:
The answer: B
References / 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 # 114
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