Considering browser compatibility, which array method would you avoid in Internet Explorer 8?
- forEach()
- map()
- filter()
- indexOf()
In terms of browser compatibility, the forEach() method should be avoided in Internet Explorer 8. This method was introduced in ECMAScript 5, and Internet Explorer 8 only supports ECMAScript 3. Other methods like map(), filter(), and indexOf() have more widespread support in older browsers.
The HTTP status code ________ indicates that the request has succeeded.
- 200 OK
- 204 No Content
- 404 Not Found
- 500 Internal Server Error
The HTTP status code 200 OK indicates that the request has succeeded. It is the standard response for successful HTTP requests. The other options represent different HTTP status codes with different meanings, such as 'No Content,' 'Not Found,' and 'Internal Server Error.'
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.
How is block scope affected when using var compared to let and const?
- var variables have block scope only within functions.
- var variables have function scope.
- let and const variables have block scope.
- let and const variables have global scope.
Variables declared with "var" in JavaScript have function scope, meaning they are only scoped to the function in which they are declared. On the other hand, "let" and "const" introduce block scope, meaning they are scoped to the nearest enclosing block, like loops or conditionals. This block-level scoping behavior prevents issues like variable hoisting and improves code maintainability.
What will be the length of the array after [1, 2, 3].unshift(4, 5);?
- 2
- 3
- 4
- 5
The length of the array will be 5. The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array. In this case, it adds 4 and 5 to the beginning of the array, making it [4, 5, 1, 2, 3], so the length is 5.
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.