Promises

The video introduces promises in JavaScript, explaining their role in managing asynchronous code and how they improve upon the callback pattern. It covers the syntax of promises, their advantages, and the semantics of resolve and reject. The video also discusses promise states like pending, fulfilled, and rejected, and compares them to callbacks, highlighting clearer semantics and error handling. The tutorial concludes with a promise example and a preview of using promises with MongoDB.

Why were promises introduced in JavaScript?

• To replace synchronous code

• To manage asynchronous code more effectively

• To simplify variable declarations

• To eliminate the need for functions

What is the first step in setting up the environment for working with promises?

• Installing a new library

• Writing a synchronous function

• Setting up a new file for promises

• Creating a new database

In the callback pattern, what is the purpose of the first argument in the callback function?

• To handle errors

• To initialize a variable

• To store the result

• To define a new function

What is the main difference between resolve and reject in promises?

• Both are used for success

• Resolve is for success, reject is for errors

• Both are used for errors

• Resolve is for errors, reject is for success

Which method is used to handle successful promise resolution?

• .catch()

• .finally()

• .then()

• .error()

What is one advantage of using promises over callbacks?

• Promises are easier to write

• Promises are faster

• Promises eliminate all errors

• Promises have clearer semantics

What happens if both resolve and reject are called in a promise?

• The promise will ignore both

• The promise will crash

• The promise will execute both

• Only the first call will be considered

What is the state of a promise before resolve or reject is called?

• Fulfilled

• Rejected

• Pending

• Completed

How does the promise pattern improve error handling compared to callbacks?

• By using a single function for all outcomes

• By separating success and error handling into different functions

• By eliminating the need for error handling

• By using synchronous code

What term describes a promise that has neither been resolved nor rejected?

• Rejected

• Pending

• Completed

• Fulfilled