A ________ object represents a group of response headers, allowing you to query them and take different actions depending on the results.
- a) XMLHttpRequest Object
- b) FetchEvent Object
- c) Headers Object
- d) Worker Object
A Headers object represents a group of response headers. It allows you to query and manipulate these headers, which can be crucial when you need to inspect or modify headers in HTTP responses. You can use it for tasks like checking for specific headers or adding custom headers to a request.
In JavaScript, variables declared with the var keyword have _________ scope.
- Block
- Local
- Global
- Function
In JavaScript, variables declared with the var keyword have global scope. This means they are accessible throughout the entire function or script, regardless of where they are declared within that function or script. It's important to be cautious when using var to avoid unintended global variable declarations.
In a code review, you spot the line const arr = [10, 20, 30]; followed by arr = [40, 50, 60];. What will be the outcome when this code is executed?
- It will result in an error.
- The arr variable will now reference [40, 50, 60].
- The original array [10, 20, 30] will be modified.
- It will create a new variable arr with [40, 50, 60].
The code will result in an error. When you declare a variable using const, it cannot be reassigned to a different value or reference. Attempting to reassign arr to [40, 50, 60] will throw a "TypeError" because it violates the immutability of const variables.
If you are developing a real-time application where any blocking of the event loop can lead to critical issues, how might you implement a "for" loop to process an array of data without introducing any blockage?
- Use for...of loop
- Use setInterval to break up iterations
- Use for...in loop
- Use a synchronous for loop with a delay
In a real-time application, using a for...of loop is the recommended approach because it doesn't block the event loop. It iterates through the array without causing delays. Using setInterval is not suitable for processing an array as it introduces an asynchronous behavior. for...in loop is used for object iteration, and a synchronous for loop with a delay would still block the event loop.
What is the drawback of using "inheritance" through the prototype chain?
- Limited support for multiple inheritance
- Increased memory consumption
- Difficulty in understanding and debugging
- Inability to create encapsulated objects
One drawback of using "inheritance" through the prototype chain in JavaScript is limited support for multiple inheritance. JavaScript does not support multiple inheritance directly, meaning an object cannot inherit from multiple prototypes simultaneously. This limitation can lead to complex workarounds or potential conflicts when trying to inherit from multiple sources. While it's possible to implement multiple inheritance in JavaScript using mixins or other patterns, it's not as straightforward as in some other programming languages.
A callback function is passed as an ________ to other functions and is executed after its parent function has completed.
- argument
- object
- attribute
- expression
A callback function is passed as an "argument" to other functions in JavaScript. It is a function that is executed after its parent function has completed its execution. This allows for asynchronous operations and event handling in JavaScript.
Which method returns a promise that resolves with the result of parsing the body text as JSON?
- .json() method
- .text() method
- .body() method
- .parseJSON() method
The .json() method of a Response object returned by fetch parses the response body text as JSON and returns a Promise that resolves with the parsed data. This method is commonly used when making API requests to obtain structured data in JSON format. The .text() method returns the response body as plain text, while .body() does not exist, and .parseJSON() is not a standard method in JavaScript.
The createElement method is used to create a new element in the _________.
- browser
- JavaScript
- document
- DOM
The createElement method in JavaScript is used to create a new HTML element within the Document Object Model (DOM). It allows you to dynamically create HTML elements that can be added to the web page or modified as needed.
How can one emulate the functionality of a switch statement using objects and functions in JavaScript?
- By creating an object where each property maps to a case label, and the corresponding values are functions to execute.
- By using a for loop to iterate through cases and execute corresponding functions.
- By using the "continue" keyword in a loop to simulate case behavior.
- By creating an array of functions, where each function corresponds to a case label.
To emulate the functionality of a switch statement in JavaScript, you can create an object where each property represents a case label, and the corresponding property values are functions that perform the desired actions. You can then use the input value to access the appropriate function from the object, effectively simulating switch behavior.
How do arrow functions handle arguments in comparison to traditional functions?
- Arrow functions don't have access to arguments.
- Arrow functions handle arguments the same way as traditional functions.
- Arrow functions receive arguments as a separate object.
- Arrow functions receive arguments as individual parameters.
Arrow functions do not have access to the arguments object like traditional functions do. Instead, they handle arguments the same way as regular functions if you explicitly define parameters. Each parameter corresponds to an argument passed to the function, allowing you to access them directly within the function body. The absence of the arguments object can be a limitation in certain scenarios.