Consider a function that fetches user information from an API. If the API call fails, you want to log an error message and then continue the execution of the function without throwing an exception to the outer scope. Which Promise method should you use to achieve this?
- Promise.catch()
- Promise.finally()
- Promise.reject()
- Promise.resolve()
You should use Promise.catch() to handle errors in a Promise. This method allows you to specify a callback function that will be called when the Promise is rejected, allowing you to log an error message and gracefully continue execution without propagating the error to the outer scope.
To remove a child element, you should use the removeChild method on the _________ element.
- parent
- child
- document
- sibling
To remove a child element from the DOM using JavaScript, you should use the removeChild method on the parent element that contains the child you want to remove. The removeChild method doesn't directly operate on the child element itself.
The _______ pattern allows a new object to be created by cloning an existing object to avoid the overhead of creating an object from scratch.
- Singleton
- Prototype
- Decorator
- Observer
The Prototype pattern allows a new object to be created by cloning an existing object, avoiding the overhead of creating an object from scratch. It involves creating an object as a prototype and then creating new instances by copying that prototype.
Given the short-circuiting nature of logical operators in JavaScript, what will be the output of the expression false && someUndeclaredVariable?
- FALSE
- TRUE
- Throws an error
- undefined
JavaScript's logical operators like && and
How does the await keyword manage the Promise’s resolve value?
- It changes the resolve value to a boolean.
- It extracts the resolve value from the Promise.
- It modifies the Promise's behavior.
- It cancels the Promise.
The 'await' keyword is used in async functions to pause the execution until the Promise is resolved. When the Promise resolves, the 'await' expression returns the resolved value. It doesn't change the value to a boolean or modify the Promise itself. This behavior is crucial for handling asynchronous operations more effectively.
You are tasked with refactoring a piece of legacy code where a function declaration within a conditional block is causing inconsistent behavior across different JavaScript engines. What is a potential solution to ensure consistent behavior?
- Use a function expression instead of a declaration within the conditional block.
- Ensure the function is declared with the 'let' keyword.
- Wrap the function declaration in a try-catch block to handle any errors.
- Split the code into multiple conditional blocks.
To ensure consistent behavior across different JavaScript engines, it's advisable to use a function expression within a conditional block instead of a function declaration. Function declarations are hoisted to the top of their containing function or script, which may lead to inconsistent results in legacy code.
In JavaScript, the "this" keyword inside an arrow function is defined by its _________ context.
- Global
- Lexical
- Local
- Execution
In JavaScript, the "this" keyword inside an arrow function is defined by its lexical context. Unlike regular functions, arrow functions do not have their own "this" binding, so they inherit the "this" value from the surrounding code block, which is determined by the lexical scope.
Which method can be used to stop the event from propagating in the capturing or bubbling phase?
- event.stopPropagation()
- event.preventDefault()
- event.stopPropagationPhase()
- event.cancelPropagation()
The event.stopPropagation() method is used to stop the event from propagating further in the DOM tree. It prevents both capturing and bubbling phases, ensuring that the event doesn't trigger any other event listeners on the same element or its ancestors. This can be helpful in controlling event flow.
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.
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.