JSFiddle - React, Tailwind, and code Playground

JavaScript

var module = (function(){
    // private property
    var number = 0;

    // global method
    _privateIncrement = function(){
        number++;
    };

    // public api
    return {
        // OK
        getNumber: function(){
             return number;   
        },
        // OK
        incrNumber: function(){
             number++;  
        },
        // Does work!
        privateIncrNumber: function(){
            _privateIncrement();
        }
    };
})();

// Show default value
document.body.innerHTML += (module.getNumber());
// Increment
module.privateIncrNumber();
// Show new value
document.body.innerHTML += (module.getNumber());
// Increment (since _privateIncrement was defined as a global!)
_privateIncrement();
// Show new value
document.body.innerHTML += (module.getNumber());

// Output: 012