How does JavaScript implement inheritance internally?
- Through classes and interfaces
- Using a prototype chain and object delegation
- By creating abstract base classes
- Through function overloading
JavaScript implements inheritance through a prototype chain and object delegation. Each object has a prototype object, and if a property or method is not found on the object itself, it's looked up on the prototype chain. This mechanism allows objects to inherit properties and methods from their prototypes, facilitating code reuse and object-oriented programming in JavaScript. Classes and interfaces are not directly related to inheritance in JavaScript.
Which early browser first implemented JavaScript?
- Internet Explorer
- Mosaic
- Netscape Navigator
- Opera
JavaScript was first implemented in Netscape Navigator. Brendan Eich developed it in 1995 while working at Netscape Communications. This move by Netscape added a significant interactive element to the web and contributed to the rapid adoption of JavaScript.
How does the for...of loop handle string iteration?
- It iterates over each character in the string.
- It treats the string as an iterable object.
- It only works on single-character strings.
- It throws an error when used with strings.
The for...of loop handles string iteration by iterating over each character in the string. It treats the string as an iterable object where each character is an element, allowing you to loop through and process individual characters in a string efficiently.
What is the purpose of the default case in a switch statement?
- It defines a fallback case
- It specifies the first case
- It is used for loop control
- It marks the end of the switch
The default case in a switch statement serves as a fallback option. If none of the other cases match the expression's value, the code in the default case block is executed. This ensures that there is always a valid path in the switch.
Which of the following scenarios is NOT recommended for using arrow functions?
- As event handlers in the DOM.
- As methods within objects.
- In callbacks where "this" context matters.
- In short, simple functions.
Arrow functions are not recommended for use as event handlers in the DOM. This is because the value of "this" in an arrow function is not determined by the event but instead retains the value from its enclosing lexical context, which may not be what you expect in an event handler. Traditional functions are usually preferred for event handlers.
How does JavaScript support lexical scoping?
- By creating global variables
- Through the use of the 'var' keyword
- By nesting functions
- By using block-level scoping with 'let'
JavaScript supports lexical scoping by allowing functions to access variables defined in their containing (enclosing) functions. This means that inner functions can "see" and use variables from outer functions, creating a chain of scope. This is achieved by nesting functions. Modern JavaScript also introduced 'let' for block-level scoping.
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.
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.