In this example we will see how closure are memory efficient

closure_memory_efficient.js

function withOutClosure(index) {
  const arr = new Array(8000).fill('Lorem ipsum olorem'); // some random heavy operation that generate data
  return arr[index];
}

withOutClosure(543);
withOutClosure(6543);
withOutClosure(345);
withOutClosure(135);

//In above each when function is called our data set is created and then when function execution finishes the function is removed from the 
// the stack as well as the data is removed as it is not referenced anywhere else so the garbage collector will remove the variable
// It is not memory efficent because every time the function is called the heavy operation is executed to generate the data set which is 
// not efficient. Here Closue comes to rescue

function withClosure() {
  const arr = new Array(8000).fill('Lorem ipsum olorem'); // some random heavy operation that generate data
  return function(index) {
    return arr[index];
  }
}

const findFromIndex = withClosure();
findFromIndex(20);
findFromIndex(290);
findFromIndex(4567)

// Here the variable array is created once and on each execution of findFromIndex we are refrencing arr variable from closure.