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.
A _______ function is a function that accepts up to three arguments: the value of the element, the index of the element, and the array object being traversed.
- callback
- handler
- middleware
- delegate
In JavaScript, a callback function is a function that can be passed as an argument to another function. Callback functions can accept up to three arguments: the value of the element, the index of the element, and the array object being traversed. They are commonly used in asynchronous programming and array methods.
In JavaScript, the Symbol data type can be used to create _________.
- Objects
- Functions
- Unique identifiers
- Private variables
In JavaScript, the Symbol data type can be used to create unique identifiers. Symbols are often used as object property keys when you need to ensure that the key is unique and not accidentally overwritten. They are not used to create objects, functions, or private variables.
What does the "this" keyword refer to in JavaScript?
- The current function
- The parent object
- The global object
- The previous function call
In JavaScript, the "this" keyword typically refers to the parent object, which is the object that calls the function. It allows you to access and manipulate the properties and methods of that object within the function. This behavior is crucial for object-oriented programming in JavaScript.
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.
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, 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.
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.
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.
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
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.
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.