What is a 'Closure'?

Question

I asked a question about Currying and closures were mentioned. What is a closure? How does it relate to currying?

Answer 1

Currying : It allows you to partially evaluate a function by only passing in a subset of its arguments. Consider this:

function multiply (x, y) {
  return x * y;
}

const double = multiply.bind(null, 2);

const eight = double(4);

eight == 8;

Closure: A closure is nothing more than accessing a variable outside of a function's scope. It is important to remember that a function inside a function or a nested function isn't a closure. Closures are always used when need to access the variables outside the function scope.

function apple(x){
   function google(y,z) {
    console.log(x*y);
   }
   google(7,2);
}

apple(3);

// the answer here will be 21