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| Section | Weight | Objectives |
|---|---|---|
| Debugging and Error Handling | 7% | - Console methods and logging - Debugging tools and breakpoints - Error types and exception handling - Defensive programming practices |
| Server-Side JavaScript | 8% | - Node.js fundamentals and runtime - Command-line tools and scripts - Core Node.js modules - Module system and require/import |
| Asynchronous Programming | 13% | - Callbacks and callback hell - Fetch API and HTTP requests - Promises and chaining - Event loop and micro/macro tasks - Async/await syntax |
| Testing | 7% | - Test doubles and mocks - Code coverage and best practices - Testing frameworks and assertions - Unit testing concepts |
| Variables, Types, and Collections | 23% | - Type coercion and conversion rules - Working with strings, numbers, dates, and booleans - Array methods and data manipulation - Variable declaration and initialization - Truthy and falsy values - JSON parsing and usage |
| Objects, Functions, and Classes | 25% | - Closures and execution context - Class syntax, inheritance, and prototypes - Function definitions, parameters, and scope - Modules and imports/exports - Decorators and advanced function patterns - Object creation, properties, and methods |
| Browsers and Events | 17% | - Document Object Model (DOM) manipulation - Browser APIs and Web Storage - Window and document object properties - Event handling, propagation, and delegation - Script loading and execution order |
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NEW QUESTION # 70
A developer is debugging a web server that uses Node.js The server hits a runtimeerror
every third request to an important endpoint on the web server.
The developer added a break point to the start script, that is at index.js at he root of the
server's source code. The developer wants to make use of chrome DevTools to debug.
Which command can be run to access DevTools and make sure the breakdown is hit ?
Answer: C
NEW QUESTION # 71
A developer has two ways to write a function:
Option A:
01 function Monster() {
02 this.growl = () = > {
03 console.log( " Grr! " );
04 }
05 }
Option B:
01 function Monster() {};
02 Monster.prototype.growl = () = > {
03 console.log( " Grr! " );
04 }
After deciding on an option, the developer creates 1000 monster objects. How many growl methods are created with Option A and Option B?
Answer: C
Explanation:
Option A:
* this.growl = () = > { ... } inside the constructor creates a new function per instance .
* For 1000 new Monster(), you get 1000 distinct growl functions , each stored on the instance itself.
Option B:
* Monster.prototype.growl = () = > { ... } attaches growl to the prototype.
* All instances share the same single growl function via the prototype chain.
* For 1000 instances, only 1 growl method exists in memory.
So: Option A # 1000; Option B # 1.
NEW QUESTION # 72
Which statement accurately describes an aspect of promises?
Answer: C
NEW QUESTION # 73
Refer to the code below:
01 let o = {
02 get js() {
03 let city1 = String( ' St. Louis ' );
04 let city2 = String( ' New York ' );
05
06 return {
07 firstCity: city1.toLowerCase(),
08 secondCity: city2.toLowerCase(),
09 }
10 }
11 }
What value can a developer expect when referencing o.js.secondCity?
Answer: B
Explanation:
1. Getter Functions in JavaScript
In JavaScript, when an object uses the get keyword, it defines a getter method . Accessing a getter property executes the function and returns its value. Thus:
o.js
does not return the getter function; instead, it executes the function located at:
get js() { ... }
and returns the object inside the return block.
2. Behavior of String() and toLowerCase()
Inside the getter:
let city1 = String( ' St. Louis ' );
let city2 = String( ' New York ' );
String() creates a string value.
Then, the returned object is constructed as:
{
firstCity: city1.toLowerCase(),
secondCity: city2.toLowerCase(),
}
The method toLowerCase() is a standard JavaScript string method that returns a new string with all alphabetic characters converted to lowercase .
Therefore:
city2.toLowerCase()
returns:
' new york '
3. Referencing the Property
When the developer writes:
o.js.secondCity
the following happens:
* The getter js runs and returns an object.
* The returned object includes the property:
secondCity: ' new york '
* Accessing .secondCity retrieves the lowercase string ' new york ' .
Therefore, the correct value is ' new york ' .
Why the Other Options Are Incorrect
A). undefined - incorrect because the property secondCity clearly exists in the returned object.
B). An error - incorrect because no invalid operations occur; all methods and properties are valid.
C). ' New York ' - incorrect because toLowerCase() transforms the string to lowercase.
JavaScript Knowledge References (Text-Based)
* Getter methods using the get keyword return computed values when accessed.
* JavaScript String values support the toLowerCase() method, which returns a lowercase version of the original string.
* Accessing nested properties like o.js.secondCity triggers the getter, returning the constructed object.
NEW QUESTION # 74
A team at Universal Containers works on a big project and uses yarn to manage 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: C
Explanation:
In JavaScript server-side development using Node.js, dependency management is typically handled through package managers such as npm or yarn . These tools categorize installed packages into:
* dependencies - required for running the application in any environment
* devDependencies - required only during development (testing tools, build tools, documentation generators, etc.) When a package is installed using:
yarn add < package > --dev
it is placed under the " devDependencies " section of package.json.
Behavior of Production Mode
Node.js uses the environment variable:
NODE_ENV=production
When this environment variable is set to production, both npm and Yarn follow the standard Node.js convention and skip installing devDependencies . This is done to optimize production builds and reduce deployment size. This is a known and documented behavior in Node.js package management tools.
Therefore, if:
* The developer added the date-manipulation library as a dev dependency , and
* Other team members execute yarn in an environment where NODE_ENV=production is set, then Yarn will not install that dependency because devDependencies are intentionally excluded in production mode.
This explains the behavior described in the question.
Why the Other Options Are Incorrect
Option A:
" YARN_ENV is set to production " is incorrect because Yarn does not use the variable YARN_ENV for dependency installation behavior. Node.js tools use NODE_ENV , not YARN_ENV.
Option B:
This is incorrect because Yarn automatically writes dependencies into package.json. Unlike older npm versions, there is no need for the --save flag.
Option D:
There is no such option as --add. The correct syntax is simply:
yarn add < package >
Missing an option that does not exist cannot be the cause.
JavaScript Knowledge References
* Node.js uses the environment variable NODE_ENV to determine production or development mode.
* Package managers (npm and Yarn) follow the rule that when NODE_ENV=production , only " dependencies " are installed and " devDependencies " are skipped.
* Yarn automatically persists installed packages to package.json without requiring --save.
* Yarn uses the command yarn add to add dependencies; there is no --add flag.
NEW QUESTION # 75
......
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