JavaScript Closure Interview Questions

There are several advantages of using closures in JavaScript. Some of them are:

• Closure enables the use of nested functions that are used to get the values created in the execution context of that of the parent function.
• They can prove as a perfect solution while solving a problem of hierarchy in any program.
• They have huge importance as far as functional programming is concerned. It solves the for loop problem of functional programming.
• It is also used to simulate private scope for variables.

An object that is able to produce a single value sometime in the future is known as Promise. The single value may either be a resolved value, or it can be a reason that it’s not resolved. There can be three states in which Promise can be:

• Fulfilled
• Reject
• Pending

There can be callbacks that can be attached to handle the fulfilled value or the rejection’s reason, this can be done by the Promise users.