_________ is the organization that now oversees the ECMAScript specification, which serves as the basis for JavaScript.
- W3C
- Mozilla
- ECMA International
- ISO
ECMA International is the organization that now oversees the ECMAScript specification, which serves as the basis for JavaScript. ECMAScript is the standardized version of JavaScript that various browsers implement.
When using a do-while loop, the loop will always execute at least ________ time(s).
- 0
- 1
- 2
- 3
When using a do-while loop, the loop will always execute at least '1' time. This is because the loop condition is checked after the loop body has executed, so it will execute at least once before checking the condition for subsequent iterations.
When defining a method in an object, the function associated with a property is referred to as a _________.
- variable
- constructor
- function
- method
When defining a method in an object, the function associated with a property is referred to as a function. Methods are functions that are properties of objects. They allow you to perform actions or calculations using the data and context within the object. Understanding methods is fundamental in object-oriented programming with JavaScript.
In a UI with nested dropdown menus, a developer wants to ensure that clicking a nested menu item does not trigger the click event of its parent menu. What method can be used to stop the event from reaching the parent menu?
- event.stopPropagation()
- event.preventDefault()
- event.stopImmediatePropagation()
- event.cancelBubble()
To prevent the event from reaching the parent menu when clicking a nested menu item, you can use the event.stopPropagation() method. This will stop the event from propagating up the DOM tree and prevent the parent menu's click event from being triggered. event.preventDefault() is used to prevent the default behavior of an event, not to stop event propagation.
What is the main difference between function declaration and function expression in JavaScript?
- Function declarations are hoisted, while function expressions are not.
- Function expressions can be named or anonymous, while function declarations must have a name.
- Function declarations are used for defining methods in objects, while function expressions are used for standalone functions.
- Function expressions are more efficient than function declarations.
The primary difference between function declaration and function expression in JavaScript is hoisting. Function declarations are hoisted, which means they are moved to the top of their containing scope during compilation. This allows you to call the function before it's declared in your code. Function expressions, on the other hand, are not hoisted, so they can only be used after their declaration in the code. Understanding this difference is crucial for managing the order of function calls in your JavaScript programs.
In which scenario might a closure be particularly useful?
- When you want to declare a global variable.
- When you want to protect variables from being modified.
- When you need to maintain access to local variables after the parent function has finished.
- When you want to create a private method in an object.
Closures in JavaScript are particularly useful when you want to create private variables or methods in an object. They allow you to maintain access to local variables even after the parent function has completed its execution. Closures help with data encapsulation and information hiding.
In a Node.js application, you need to perform several database operations consecutively, where each operation depends on the result of the previous one. How might you structure your asynchronous code to handle this scenario efficiently?
- Use Promises and "Promise.all"
- Utilize nested callbacks
- Implement async generators
- Employ event emitters
To efficiently handle consecutive database operations with dependencies in Node.js, you can structure your asynchronous code using Promises and "Promise.all." This approach allows you to create Promises for each operation and then use "Promise.all" to wait for all Promises to resolve. It ensures that operations execute in the correct order and that you can handle dependencies between them easily.
Which method is used to handle the successful resolution of a Promise?
- .then()
- .catch()
- .finally()
- .resolve()
To handle the successful resolution of a Promise, you use the .then() method. This method allows you to specify what should happen once the Promise is fulfilled or successfully resolved. It takes a callback function as its argument, which gets executed when the Promise is resolved.
How does JavaScript’s prototype inheritance differ from classical inheritance models?
- JavaScript uses prototype-based inheritance, allowing objects to inherit directly from other objects.
- JavaScript's prototype inheritance is dynamic and allows objects to change their prototype during runtime.
- In classical inheritance, classes define objects, while JavaScript's prototype inheritance relies on objects and their prototypes.
- JavaScript's prototype chain is single, while classical inheritance can involve multiple parent classes.
JavaScript's prototype inheritance is dynamic, which means you can modify an object's prototype at runtime, adding or removing properties and methods. Classical inheritance is typically static, where classes define the structure beforehand. This dynamic nature allows for greater flexibility but can also lead to unexpected behaviors if not managed properly.
You're building a weather application and you're using the Fetch API to request weather data from a third-party API. However, you realize that the application does not properly handle when the API is down. How would you handle this to inform the user?
- Implement a try-catch block to catch network errors and display a user-friendly message.
- Use the finally block to handle any errors and show an alert to the user.
- Utilize the window.onerror event to detect API failures and log them.
- Set up a timer to periodically check the API status and notify the user if it's down.
To handle API failures and inform the user, you should implement a try-catch block around the fetch request. This allows you to catch network errors, like when the API is down, and then display a user-friendly message or take appropriate action. The other options are not recommended for handling API failures effectively.