Example of how you can use closure to expose private members

closure-example.js

function Closure() {
    var number = 0;

    // Manipulate the private member directly
    function makeLower() {
        number--;
        console.log(number);
    }

    // Manipulate the private member directly
    function makeHigher() {
        number++;
        console.log(number);
    }

    // Reassign the value of the private member
    function reset() {
        number = 0;
        console.log(number);
    }

    // Prevent anything from being modified
    return Object.freeze({
        makeLower: makeLower,
        makeHigher: makeHigher,
        reset: reset
    });
}

// Usage
var c = Closure();

c.makeHigher(); // 1
c.makeHigher(); // 2
c.makeHigher(); // 3
c.makeLower();  // 2
c.reset();      // 0
c.makeLower();  // -1
c.makeLower();  // -2


// Array Example
function ArrayClosure() {
    var arr = [];

    function addElement(e) {
        arr.push(e);
        console.log(arr);
    }

    function removeElement(e) {
        var i = arr.indexOf(e);
        arr = arr.slice(0, i).concat(arr.slice(i + 1, arr.length));
        console.log(arr);
    }

    function reset() {
        arr = [];
        console.log(arr);
    }

    return Object.freeze({
        addElement: addElement,
        removeElement: removeElement,
        reset: reset
    });
}

var a = ArrayClosure();
a.addElement(0);        // [0]
a.addElement(1);        // [0, 1]
a.addElement(2);        // [0, 1, 2]
a.addElement(3);        // [0, 1, 2, 3]
a.removeElement(2);     // [0, 1, 3]
a.reset();              // []
a.addElement(4);        // [4]
a.addElement(5);        // [4, 5]