20 Call, Apply, Bind Interview Questions and Answers

If you are interviewing for a position that involves JavaScript, you may be asked about call, apply and bind. These are all methods that can be used to invoke a function and set the value of this. Knowing how and when to use each method is important for any JavaScript developer. In this article, we will review some common interview questions about call, apply and bind so that you can be prepared for your next job interview.

Call, Apply, Bind Interview Questions and Answers

Here are 20 commonly asked Call, Apply, Bind interview questions and answers to prepare you for your interview:

1. What is the difference between call, apply and bind functions?

The main difference between the call, apply and bind functions is that the call function immediately invokes the function it is called on, whereas the apply and bind functions return a new function that can be invoked at a later time. The apply function is similar to the call function, but it expects the arguments to be passed in as an array. The bind function is used to create a new function with the same this value as the function it is called on.

2. How do you use a call function to change the context of an object reference inside a function?

You can use the call function to change the context of an object reference inside a function by using the call function to explicitly set the value of this inside the function. For example:

function myFunction() {
console.log(this); // outputs the global object
}

myFunction.call(null); // outputs the global object

In this example, the call function is used to set the value of this inside the function to null. This means that when the function is executed, this will refer to the global object.

3. Can you explain what partial functions are in JavaScript?

A partial function is a function that takes one or more arguments, but not all of the arguments that it could take. This allows you to create a new function that is based on an existing function, but with different arguments. This can be useful when you want to reuse a function but with different data.

4. How can you create your own custom bind function?

There are a few different ways to create a custom bind function. One way would be to use the Function.prototype.bind method. Another way would be to create a function that returns a new function with the desired context.

Here is an example of using the Function.prototype.bind method:

function myBind(func, context) {
return func.bind(context);
}

And here is an example of creating a function that returns a new function with the desired context:

function myBind(func, context) {
return function() {
return func.apply(context, arguments);
}
}

5. How can you make sure that a function always returns a value even if it’s called with new?

You can use the .bind() method to make sure that a function always returns a value even if it’s called with new. The .bind() method will bind the function to the specified object, and ensure that the function always returns the specified object.

6. How would you implement inheritance using the call() method?

The call() method can be used to invoke a function with a given this value and arguments provided as an array (or an array-like object). So, to implement inheritance using the call() method, you would need to write a function that takes in the child class and the parent class as parameters. The child class would then be invoked using the call() method, with the parent class being passed as the this value. This would give the child class access to the parent class’s methods and properties.

7. How do you combine two different objects into one using the call() method?

The call() method can be used to combine two different objects into one. The first object will be the object that you want to combine with the second object. The second object will be the object that you want to use as the base for the new object. The call() method will return a new object that is a combination of the two objects.

8. How do you make sure a certain piece of code gets executed after another specific piece of code?

In order to make sure that one piece of code gets executed after another, you can use the call, apply, or bind methods. The call method will execute the code immediately, while apply will execute the code in the next available execution cycle. Bind will bind the code to a specific object, making it available to be executed later.

9. How would you simulate currying using the call() method?

Currying is a process of creating a new function by binding some arguments to an existing function. The call() method can be used to bind arguments to a function, and thus can be used to simulate currying. For example, if you have a function that takes two arguments, you can use call() to bind the first argument to the function and create a new function that only takes the second argument. This new function can then be invoked with the second argument to get the same result as if the original function had been invoked with both arguments.

10. Can you give me some examples of how the bind() method can be used?

The bind() method can be used in a number of ways, but one of the most common is to bind a function to a specific object. This can be useful if you want to ensure that a function always uses a specific object as its this value. For example, you could use bind() to make sure that a function always used a certain DOM element as its this value.

11. What are the differences between setTimeout(), setInterval(), and requestAnimationFrame()?

The main difference between setTimeout(), setInterval(), and requestAnimationFrame() is that setTimeout() and setInterval() are used to schedule a task to be executed after a delay, while requestAnimationFrame() is used to schedule a task to be executed before the next repaint of the screen.

setTimeout() is typically used when you want to execute a task once after a delay. For example, you might use setTimeout() to display a popup message after a user has been on a page for 5 seconds.

setInterval() is typically used when you want to execute a task repeatedly at regular intervals. For example, you might use setInterval() to refresh a page every 30 seconds.

requestAnimationFrame() is typically used when you want to execute a task before the next repaint of the screen. For example, you might use requestAnimationFrame() to animate a series of images on a page.

12. Why should we use requestAnimationFrame() instead of setInterval() or setTimeout()?

requestAnimationFrame() is a newer function that is specifically designed for animations. It tells the browser that you are going to be performing an animation and that the browser should optimize accordingly. This means that it will wait until the next screen refresh before calling the function again, which can help to improve performance. setInterval() and setTimeout() are older functions that are not as optimized for animations and can cause issues with performance.

13. Can you design a module pattern by passing callbacks as arguments to functions?

Yes, you can design a module pattern by passing callbacks as arguments to functions. This is a good way to create modular code that can be reused in different contexts.

14. Is there any way to pass multiple parameters to a callback function without modifying its signature?

Yes, there are several ways to do this. One way is to use the bind() method to bind the function to an object, and then pass in the parameters as additional arguments to the bind() method. Another way is to use the call() or apply() method to directly invoke the function with the desired arguments.

15. How do you ensure that every callback function you write has access to a given variable?

You can use the .bind() method on a function to “bind” it to a given variable. This will ensure that the function always has access to that variable, no matter where it is invoked.

16. What is the best way to find out whether a number is prime or not?

There is no definitive answer to this question, as there are multiple ways to determine whether a number is prime or not. However, one common method is to use the Sieve of Eratosthenes. This involves creating an array of all numbers up to the number in question, and then eliminating all numbers that are not prime.

17. What does “this” mean in the context of JavaScript?

“This” in JavaScript refers to the object that is currently being processed. In the context of a function, “this” refers to the object that is calling the function.

18. What is the purpose of the _bind_ method in Underscore.js?

The _bind_ method in Underscore.js is used to bind a function to an object, meaning that whenever the function is called, the this keyword will refer to the object that the function is bound to. This can be useful when you want to ensure that a callback function is always executed in the context of a particular object.

19. How do you convert string values to JSON format in JavaScript?

You can use the JSON.parse() method to convert a string value to JSON format.

20. What is the fastest way to remove duplicate items from an array in JavaScript?

The fastest way to remove duplicate items from an array in JavaScript is to use the Set data structure. The Set object lets you store unique values of any type, whether primitive values or object references.