While working on a project, you found out that the API you are fetching data from sends relevant error messages in the body of the response, even when the request fails. How do you extract and use this error message in JavaScript?
- Check the response.ok property to determine success and use response.statusText for error messages.
- Use the response.error property to access the error message.
- Parse the entire response body as a JSON object and access the error message field.
- Create a custom error handler function to retrieve the error message from the API.
To extract and use error messages from the API response, you should check the response.ok property to determine success or failure. If it's a failure, you can access the error message using response.statusText. The other options are not the standard way to extract error messages from a fetch response.
How do you ensure that dynamically added elements maintain accessibility features, like ARIA roles?
- Dynamically set ARIA roles using JavaScript after adding the element.
- Browsers automatically assign appropriate ARIA roles to new elements.
- Dynamically added elements cannot have ARIA roles.
- Add ARIA roles directly in the HTML source code.
To ensure that dynamically added elements maintain accessibility features like ARIA roles, you should dynamically set ARIA roles using JavaScript after adding the element. Browsers don't automatically assign ARIA roles, and adding roles directly in the HTML source code isn't dynamic. Option 3 is incorrect.
Unlike traditional functions, arrow functions do not have their own __________.
- this
- arguments
- return
- parameters
Unlike traditional functions, arrow functions do not have their own this binding. In arrow functions, this retains the value of the enclosing lexical context, which makes it useful in cases where you want to maintain the context of the surrounding code, such as in callbacks or when defining functions within functions.
You're debugging a JavaScript application and notice unexpected behavior in the manipulation of an array. The items are not being removed correctly using a method, and it turns out the array is not being modified at all. Which array method might be mistakenly being used?
- pop()
- push()
- splice()
- concat()
The concat() method is often mistakenly used for removing elements from an array because it doesn't modify the original array but returns a new array instead. The correct method for removing elements from an array is splice() or other methods like pop() or shift().
What is "Promise chaining" in JavaScript?
- A method for nesting multiple if statements
- A technique for connecting multiple Promises
- A way to synchronize asynchronous functions
- A method to define variables
"Promise chaining" is a technique in JavaScript where you can connect multiple Promises together. It allows you to execute asynchronous operations sequentially, making code more readable and manageable, especially when dealing with multiple async tasks.
How does the prototype property behave in arrow functions?
- Arrow functions have a prototype property.
- Arrow functions do not have a prototype.
- Arrow functions inherit their prototype.
- Arrow functions override their prototype.
Arrow functions do not have their own this context and do not have a prototype property. Unlike regular functions, arrow functions do not bind their own this value or have a prototype property. This is a key difference to keep in mind when choosing between regular functions and arrow functions in JavaScript.
Consider a situation where you have a switch statement inside a function, and forgetting to include a break statement leads to a bug. How might this bug manifest in the function’s behavior?
- The function might return the value associated with the first matching case, and all subsequent code within the switch block will execute as well.
- The function will throw an error, indicating a missing "break" statement, and won't execute any code within the switch block.
- The function will automatically insert "break" statements at the end of each case, ensuring correct behavior.
- The function will ignore the switch statement and continue executing the code outside of the switch block.
If you forget to include a "break" statement in a switch case, it will lead to a bug where the function may not behave as expected. Instead of stopping after the first matching case, the switch statement will "fall through" to subsequent cases, causing unintended behavior. The correct option is to use a "break" statement to exit the switch block after handling a case. JavaScript doesn't automatically insert "break" statements, and it doesn't throw an error for missing "break" statements.
The method myArray.find(callback) returns _______ if no element passes the test.
- NaN
- undefined
- an empty array
- -1
The myArray.find(callback) method returns undefined if no element in the array passes the test provided by the callback function. This is because it signifies that no element satisfies the condition. If an element is found that passes the test, it returns that element.
Which of the following is NOT a state of a Promise?
- Pending
- Resolved
- Rejected
- Completed
In JavaScript, a Promise can be in one of three states: Pending (initial state), Resolved (fulfilled with a value), or Rejected (fulfilled with an error). "Completed" is not a valid state for a Promise; it's either resolved or rejected.
An arrow function is defined using the _________ symbol.
- =>
- ->
- function
- =
An arrow function is defined using the => (fat arrow) symbol. This concise syntax is a shorthand for writing simple, one-liner functions in JavaScript. It's especially useful for functions that have no side effects and return a single expression. The => symbol distinguishes arrow functions from traditional function declarations.