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.
What is the result of the comparison operator === if the operands are of different types?
- FALSE
- TRUE
- Undefined
- Error
The comparison operator === (strict equality) in JavaScript returns true if the operands are of different types and have the same value. JavaScript performs type coercion with ==, but === strictly checks both value and type.
What is the time complexity of the unshift() method in JavaScript arrays?
- O(n)
- O(1)
- O(log n)
- O(n log n)
The unshift() method in JavaScript arrays has a time complexity of O(n), where "n" represents the number of elements in the array. This is because it needs to shift all existing elements to make room for the new element at the beginning. The higher the number of elements, the longer it takes.
Which design pattern can be used to create a family of related or dependent objects without specifying their concrete classes?
- Factory Method Pattern
- Abstract Factory Pattern
- Singleton Pattern
- Prototype Pattern
The Abstract Factory Pattern allows you to create families of related or dependent objects without specifying their concrete classes. It provides an interface for creating objects in various categories while ensuring their compatibility within the family.
Which statement is true regarding function scope in JavaScript?
- Functions can access variables from outer scopes.
- Variables declared inside functions have global scope.
- Variables declared inside functions have function scope.
- Variables declared inside functions are accessible only within that function's block.
In JavaScript, variables declared inside functions have function scope, meaning they are only accessible within that function. This is important for encapsulation and avoiding variable conflicts. Variables declared outside of functions have global scope, and functions can access variables from outer scopes, but the reverse is not true.
The _________ event does not necessarily have to be attached to a form element.
- submit
- reset
- change
- keydown
The change event in JavaScript doesn't necessarily have to be attached to a form element. It can also be used with other HTML elements like ,