Developers & Programmers Interview

Interview Question:

Can you explain the difference between "undefined" and "null" in JavaScript?

Candidate's Answer:

Undefined means the variable has been declared and has not been assigned to any value. But null is basically a value that we assign to a variable. And there's also one difference that we see from the variable point of view that if there is an undefined variable.The type of it will be.Undefined, but if we have a null type of variable, the type of it will return an object.

Evaluation:

Your answer is mostly correct, but there are some nuances that you could further explain to provide a more thorough understanding of the difference between "undefined" and "null" in JavaScript.

In JavaScript, "undefined" is a primitive value that is automatically assigned to a variable that has been declared but not yet assigned a value. On the other hand, "null" is also a primitive value, but it is explicitly assigned to a variable to indicate that it has no value.

One important distinction between the two is that while "undefined" represents the absence of a value, "null" represents a value of "nothingness." In other words, "undefined" typically signifies that a variable has not been initialized, while "null" is explicitly used to indicate that a variable has been intentionally set to have no value.

Additionally, as you mentioned, the typeof operator in JavaScript returns "undefined" for variables that are declared but not assigned a value, and "object" for variables that are explicitly assigned the value of "null."

To improve your answer, you can provide examples to illustrate the difference between "undefined" and "null" in JavaScript. You can also mention that both "undefined" and "null" are falsy values in JavaScript, meaning they will evaluate to false in a boolean context.

Overall, your answer is clear and accurate, but adding more examples and further explanations would enhance it. I would rate your answer as 4/5.

Interview Question:

How does prototypal inheritance work in JavaScript?

Candidate's Answer:

I dont know

Evaluation:

Your answer "I don't know" is not necessarily correct or appropriate for an interview question, especially if the topic is JavaScript and you're being asked about prototypal inheritance. It would be better to acknowledge that you may not know the answer, but express a willingness to learn or provide a brief overview of what you do know about the topic.

Prototypal inheritance in JavaScript refers to the mechanism by which objects can inherit properties and methods from other objects. Each object in JavaScript has a prototype, which is another object that it inherits from. When you access a property or method on an object, if it doesn't exist on that object, JavaScript will look for it on the object's prototype, and so on up the prototype chain until it finds the property or method or reaches the end of the chain.

To improve your answer, you could acknowledge that you may not know the specifics of how prototypal inheritance works in JavaScript but provide some general knowledge or understanding of the concept. You could also express an interest in learning more about the topic and how it relates to JavaScript programming.

Overall, I would rate your answer 1/5 as it does not demonstrate any knowledge or understanding of the topic and could be improved with a more thoughtful response.