What are Closures, Promises in JS?

Question

Accepted Answer

Closures are functions that have access to variables from their outer scope. Promises are objects used for asynchronous programming in JavaScript.

Closures are created when a function is defined inside another function and the inner function has access to the outer function's variables.
Closures allow for data encapsulation and private variables in JavaScript.
Promises are used to handle asynchronous operations and provide a way to handle success or failure of those operations.
Promises have states: pending, fulfilled, or rejected, and can be chained together using 'then' and 'catch' methods.
Example of closures: function outer() { var x = 10; function inner() { console.log(x); } return inner; } var closureFunc = outer(); closureFunc(); // Output: 10
Example of promises: const promise = new Promise((resolve, reject) => { setTimeout(() => { resolve('Success'); }, 2000); }); promise.then((result) => { console.log(result); }).catch((error) => { console.log(error); }); // Output after 2 seconds: Success

Accepted Answer

A closure is formed when you nest functions, inner functions can refer to the variables present in their outer enclosing functions even after their parent functions have already executed.

A Function that returns function but with lexical scope, i.e the variables will be accessible throughout the closure.

What are Closures, Promises in JS?

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