While working with React, you notice a function defined using the function keyword is not updating the component state as it should. You suspect it's related to the "this" keyword. What might be the problem?
- The function should be an arrow function
- "this" in a React component refers to the element
- "this" in a React component refers to the component
- The function lacks proper binding
In React, when using the function keyword to define a custom method within a component class, you need to manually bind the function to the component instance in the constructor using "this.functionName = this.functionName.bind(this);" to ensure that "this" refers to the component instance and not the function itself.
Unlike function expressions, function declarations are _________.
- Hoisted
- Anonymous
- Scoped
- Encapsulated
Unlike function expressions, function declarations are hoisted. This means they are moved to the top of their containing scope during compilation, allowing you to call them before they are defined in the code. Function expressions are not hoisted in the same way.
How can a subclass be created in JavaScript?
- Using the extends keyword
- By defining a new class with the same name
- Using the super keyword
- By using the inherit keyword
In JavaScript, you can create a subclass by using the extends keyword. This allows you to inherit the properties and methods of another class, forming a class hierarchy. The extends keyword establishes a relationship between the subclass and the superclass.
The ______ statement is used to specify a block of code to be executed if the condition is false.
- if-else
- else-if
- if
- switch
The "else" statement is used to specify a block of code to be executed if the condition specified in the preceding "if" statement is false. It allows for conditional execution, and if the "if" condition is not met, the code inside "else" will be executed.
Which method would you use to replace an HTML element with another?
- replaceElement()
- replaceChild()
- swapElement()
- switchElement()
The correct method to replace an HTML element with another in JavaScript is replaceChild(). This method allows you to replace a child element within a parent element. It takes two arguments: the new element to be inserted and the old element to be replaced.
In a scenario where you have to create a function that acts differently based on the type of input (string, number, or boolean), how might you implement this using a switch statement?
- Use separate case statements for each data type, and within each case, handle the specific behavior for that data type.
- Convert the input to a string, and then use a single case statement for "string", "number", and "boolean" as switch cases.
- Create individual functions for each data type and call the appropriate function based on the input type.
- Use an if-else ladder instead of a switch statement to handle different data types.
When implementing a function that acts differently based on input types using a switch statement, it's best practice to use separate case statements for each data type. This ensures clarity and maintainability of your code, as each case can handle the specific behavior for that data type. Using a single case statement with type conversion is less readable and may lead to unexpected behavior. Individual functions for each type would increase code complexity unnecessarily, and using an if-else ladder is less efficient and less idiomatic in JavaScript.
How does event looping handle while(true) in Node.js environments?
- It blocks the event loop indefinitely, causing the application to hang.
- It executes the loop in a separate thread to avoid blocking.
- It sets a maximum execution time for the loop to prevent hanging.
- It queues the while(true) in the event loop, allowing other events to execute.
In Node.js, using while(true) will block the event loop indefinitely, causing the application to hang. This is because Node.js is single-threaded and relies on an event loop to handle asynchronous tasks. Long-running synchronous code like while(true) can prevent other tasks from being executed.
In a do-while loop, when is the condition checked?
- Before executing the code block
- After executing the code block
- During the execution of the code block
- It's not checked in a do-while loop
In a do-while loop, the condition is checked after executing the code block. This means that the code block will always execute at least once before the condition is evaluated. If the condition is true after the first execution, the loop will continue running; otherwise, it will exit. This makes do-while loops suitable when you want to ensure that a specific task is performed before checking the condition.
Imagine you’re refactoring a piece of code that involves a series of callback functions into a format that uses async/await. What should you pay extra attention to regarding error handling when refactoring the code?
- Ensure proper try/catch
- Maintain callback structure
- Avoid async/await
- Ignore error handling entirely
When refactoring code to use async/await, it's crucial to ensure proper error handling. This means using try/catch blocks around await operations to catch and handle any exceptions that may occur during asynchronous operations. Neglecting error handling could lead to unhandled exceptions and unexpected behavior.
The switch statement in JavaScript uses _________ comparison to evaluate cases.
- Strict (===)
- Loose (==)
- Greater (>)
- Lesser (<)
The switch statement in JavaScript uses strict (===) comparison to evaluate cases. This means that not only the value but also the data type must match for a case to be executed. This ensures accuracy when comparing values in a switch statement.