Implement a counter function with closure, where the counter cannot be changed from outside.

Here's an example of a counter function in JavaScript using closure, where the internal counter value is inaccessible from outside and can only be changed through methods:

function createCounter() {
  let count = 0; // private variable

  return {
    increment() {
      count++;
      return count;
    },
    decrement() {
      count--;
      return count;
    },
    getValue() {
      return count;
    }
  };
}

const counter = createCounter();
console.log(counter.increment()); // 1
console.log(counter.increment()); // 2
console.log(counter.getValue());  // 2
// Cannot directly change count, for example counter.count = 100 will not affect the internal value

Thus, the variable count is encapsulated and accessible only through the object's methods.