A version of the other gist closure.js but with a simpler syntax for beginners

closures-simpler-syntax.js

function makeCounter(initialValue) {
  let count = initialValue;
  function toString() {
    return 'The count is ' + count +'.';
  }
  return {
    add: function() { return ++count },
    sub: function() { return --count },
    val: function() { return count },
    toString: toString
  };
}

var counter = makeCounter(0);
console.log(counter.add()) // 1 
console.log(counter.val()) // 1
console.log(counter.sub()) // 0
console.log(counter.add()) // 1
console.log(counter.add()) // 2
console.log(counter.toString()) // The count is 2.